initial sabre upgrade (needs lots of work - to wit: authentication, redo the browser interface, and rework event export/import)

24 files changed, 2586 insertions, 0 deletions

diff --git a/vendor/sabre/xml/.gitignore b/vendor/sabre/xml/.gitignore
new file mode 100644
index 000000000..accb586c7
--- /dev/null
+++ b/vendor/sabre/xml/.gitignore
@@ -0,0 +1,9 @@
+vendor
+composer.lock
+tests/cov
+.*.swp
+
+# Composer binaries
+bin/phpunit
+bin/php-cs-fixer
+bin/sabre-cs-fixer
diff --git a/vendor/sabre/xml/.travis.yml b/vendor/sabre/xml/.travis.yml
new file mode 100644
index 000000000..19a61a2c8
--- /dev/null
+++ b/vendor/sabre/xml/.travis.yml
@@ -0,0 +1,20 @@
+language: php
+php:
+  - 5.4
+  - 5.5
+  - 5.6
+  - 7
+  - hhvm
+
+matrix:
+  fast_finish: true
+
+sudo: false
+
+cache: vendor
+
+script:
+  - ./bin/phpunit --configuration tests/phpunit.xml.dist
+  - ./bin/sabre-cs-fixer fix . --dry-run --diff
+
+before_script: composer install
diff --git a/vendor/sabre/xml/CHANGELOG.md b/vendor/sabre/xml/CHANGELOG.md
new file mode 100644
index 000000000..3d8eb0fcb
--- /dev/null
+++ b/vendor/sabre/xml/CHANGELOG.md
@@ -0,0 +1,208 @@
+ChangeLog
+=========
+
+1.4.1 (2016-03-12)
+-----------------
+
+* Parsing clark-notation is now cached. This can speed up parsing large
+  documents with lots of repeating elements a fair bit. (@icewind1991).
+
+
+1.4.0 (2016-02-14)
+------------------
+
+* Any array thrown into the serializer with numeric keys is now simply
+  traversed and each individual item is serialized. This fixes an issue
+  related to serializing value objects with array children.
+* When serializing value objects, properties that have a null value or an
+  empty array are now skipped. We believe this to be the saner default, but
+  does constitute a BC break for those depending on this.
+* Serializing array properties in value objects was broken.
+
+
+1.3.0 (2015-12-29)
+------------------
+
+* The `Service` class adds a new `mapValueObject` method which provides basic
+  capabilities to map between ValueObjects and XML.
+* #61: You can now specify serializers for specific classes, allowing you
+  separate the object you want to serialize from the serializer. This uses the
+  `$classMap` property which is defined on both the `Service` and `Writer`.
+* It's now possible to pass an array of possible root elements to
+  `Sabre\Xml\Service::expect()`.
+* Moved some parsing logic to `Reader::getDeserializerForElementName()`,
+  so people with more advanced use-cases can implement their own logic there.
+* #63: When serializing elements using arrays, the `value` key in the array is
+  now optional.
+* #62: Added a `keyValue` deserializer function. This can be used instead of
+  the `Element\KeyValue` class and is a lot more flexible. (@staabm)
+* Also added an `enum` deserializer function to replace
+  `Element\Elements`.
+* Using an empty string for a namespace prefix now has the same effect as
+  `null`.
+
+
+1.2.0 (2015-08-30)
+------------------
+
+* #53: Added `parseGetElements`, a function like `parseInnerTree`, except
+  that it always returns an array of elements, or an empty array.
+
+
+1.1.0 (2015-06-29)
+------------------
+
+* #44, #45: Catching broken and invalid XML better and throwing
+  `Sabre\Xml\LibXMLException` whenever we encounter errors. (@stefanmajoor,
+   @DaanBiesterbos)
+
+
+1.0.0 (2015-05-25)
+------------------
+
+* No functional changes since 0.4.3. Marking it as 1.0.0 as a promise for
+  API stability.
+* Using php-cs-fixer for automated CS enforcement.
+
+
+0.4.3 (2015-04-01)
+-----------------
+
+* Minor tweaks for the public release.
+
+
+0.4.2 (2015-03-20)
+------------------
+
+* Removed `constants.php` again. They messed with PHPUnit and don't really
+  provide a great benefit.
+* #41: Correctly handle self-closing xml elements.
+
+
+0.4.1 (2015-03-19)
+------------------
+
+* #40: An element with an empty namespace (xmlns="") is not allowed to have a
+  prefix. This is now fixed.
+
+
+0.4.0 (2015-03-18)
+------------------
+
+* Added `Sabre\Xml\Service`. This is intended as a simple way to centrally
+  configure xml applications and easily parse/write things from there. #35, #38.
+* Renamed 'baseUri' to 'contextUri' everywhere.
+* #36: Added a few convenience constants to `lib/constants.php`.
+* `Sabre\Xml\Util::parseClarkNotation` is now in the `Sabre\Xml\Service` class.
+
+
+0.3.1 (2015-02-08)
+------------------
+
+* Added `XmlDeserializable` to match `XmlSerializable`.
+
+
+0.3.0 (2015-02-06)
+------------------
+
+* Added `$elementMap` argument to parseInnerTree, for quickly overriding
+  parsing rules within an element.
+
+
+0.2.2 (2015-02-05)
+------------------
+
+* Now depends on sabre/uri 1.0.
+
+
+0.2.1 (2014-12-17)
+------------------
+
+* LibXMLException now inherits from ParseException, so it's easy for users to
+  catch any exception thrown by the parser.
+
+
+0.2.0 (2014-12-05)
+------------------
+
+* Major BC Break: method names for the Element interface have been renamed
+  from `serializeXml` and `deserializeXml` to `xmlSerialize` and
+  `xmlDeserialize`. This is so that it matches PHP's `JsonSerializable`
+  interface.
+* #25: Added `XmlSerializable` to allow people to write serializers without
+  having to implement a deserializer in the same class.
+* #26: Renamed the `Sabre\XML` namespace to `Sabre\Xml`. Due to composer magic
+  and the fact that PHP namespace are case-insensitive, this should not affect
+  anyone, unless you are doing exact string matches on class names.
+* #23: It's not possible to automatically extract or serialize Xml fragments
+  from documents using `Sabre\Xml\Element\XmlFragment`.
+
+
+0.1.0 (2014-11-24)
+------------------
+
+* #16: Added ability to override `elementMap`, `namespaceMap` and `baseUri` for
+  a fragment of a document during reading an writing using `pushContext` and
+  `popContext`.
+* Removed: `Writer::$context` and `Reader::$context`.
+* #15: Added `Reader::$baseUri` to match `Writer::$baseUri`.
+* #20: Allow callbacks to be used instead of `Element` classes in the `Reader`.
+* #25: Added `readText` to quickly grab all text from a node and advance the
+  reader to the next node.
+* #15: Added `Sabre\XML\Element\Uri`.
+
+
+0.0.6 (2014-09-26)
+------------------
+
+* Added: `CData` element.
+* #13: Better support for xml with no namespaces. (@kalmas)
+* Switched to PSR-4 directory structure.
+
+
+0.0.5 (2013-03-27)
+------------------
+
+* Added: baseUri property to the Writer class.
+* Added: The writeElement method can now write complex elements.
+* Added: Throwing exception when invalid objects are written.
+
+
+0.0.4 (2013-03-14)
+------------------
+
+* Fixed: The KeyValue parser was skipping over elements when there was no
+  whitespace between them.
+* Fixed: Clearing libxml errors after parsing.
+* Added: Support for CDATA.
+* Added: Context properties.
+
+
+0.0.3 (2013-02-22)
+------------------
+
+* Changed: Reader::parse returns an array with 1 level less depth.
+* Added: A LibXMLException is now thrown if the XMLReader comes across an error.
+* Fixed: Both the Elements and KeyValue parsers had severe issues with
+  nesting.
+* Fixed: The reader now detects when the end of the document is hit before it
+  should (because we're still parsing an element).
+
+
+0.0.2 (2013-02-17)
+------------------
+
+* Added: Elements parser.
+* Added: KeyValue parser.
+* Change: Reader::parseSubTree is now named parseInnerTree, and returns either
+  a string (in case of a text-node), or an array (in case there were child
+  elements).
+* Added: Reader::parseCurrentElement is now public.
+
+
+0.0.1 (2013-02-07)
+------------------
+
+* First alpha release
+
+Project started: 2012-11-13. First experiments in June 2009.
diff --git a/vendor/sabre/xml/LICENSE b/vendor/sabre/xml/LICENSE
new file mode 100644
index 000000000..c9faf409b
--- /dev/null
+++ b/vendor/sabre/xml/LICENSE
@@ -0,0 +1,27 @@
+Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/)
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright notice,
+      this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimer in the documentation
+      and/or other materials provided with the distribution.
+    * Neither the name Sabre nor the names of its contributors
+      may be used to endorse or promote products derived from this software
+      without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+    POSSIBILITY OF SUCH DAMAGE.
diff --git a/vendor/sabre/xml/README.md b/vendor/sabre/xml/README.md
new file mode 100644
index 000000000..e6fc4db5f
--- /dev/null
+++ b/vendor/sabre/xml/README.md
@@ -0,0 +1,25 @@
+sabre/xml
+=========
+
+[![Build Status](https://secure.travis-ci.org/fruux/sabre-xml.svg?branch=master)](http://travis-ci.org/fruux/sabre-xml)
+
+The sabre/xml library is a specialized XML reader and writer.
+
+Documentation
+-------------
+
+* [Introduction](http://sabre.io/xml/).
+* [Installation](http://sabre.io/xml/install/).
+* [Reading XML](http://sabre.io/xml/reading/).
+* [Writing XML](http://sabre.io/xml/writing/).
+
+
+Support
+-------
+
+Head over to the [SabreDAV mailing list](http://groups.google.com/group/sabredav-discuss) for any questions.
+
+Made at fruux
+-------------
+
+This library is being developed by [fruux](https://fruux.com/). Drop us a line for commercial services or enterprise support.
diff --git a/vendor/sabre/xml/bin/.empty b/vendor/sabre/xml/bin/.empty
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/vendor/sabre/xml/bin/.empty
diff --git a/vendor/sabre/xml/lib/ContextStackTrait.php b/vendor/sabre/xml/lib/ContextStackTrait.php
new file mode 100644
index 000000000..ee3a3baca
--- /dev/null
+++ b/vendor/sabre/xml/lib/ContextStackTrait.php
@@ -0,0 +1,123 @@
+<?php
+
+namespace Sabre\Xml;
+
+/**
+ * Context Stack
+ *
+ * The Context maintains information about a document during either reading or
+ * writing.
+ *
+ * During this process, it may be neccesary to override this context
+ * information.
+ *
+ * This trait allows easy access to the context, and allows the end-user to
+ * override its settings for document fragments, and easily restore it again
+ * later.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+trait ContextStackTrait {
+
+    /**
+     * This is the element map. It contains a list of XML elements (in clark
+     * notation) as keys and PHP class names as values.
+     *
+     * The PHP class names must implement Sabre\Xml\Element.
+     *
+     * Values may also be a callable. In that case the function will be called
+     * directly.
+     *
+     * @var array
+     */
+    public $elementMap = [];
+
+    /**
+     * A contextUri pointing to the document being parsed / written.
+     * This uri may be used to resolve relative urls that may appear in the
+     * document.
+     *
+     * The reader and writer don't use this property, but as it's an extremely
+     * common use-case for parsing XML documents, it's added here as a
+     * convenience.
+     *
+     * @var string
+     */
+    public $contextUri;
+
+    /**
+     * This is a list of namespaces that you want to give default prefixes.
+     *
+     * You must make sure you create this entire list before starting to write.
+     * They should be registered on the root element.
+     *
+     * @var array
+     */
+    public $namespaceMap = [];
+
+    /**
+     * This is a list of custom serializers for specific classes.
+     *
+     * The writer may use this if you attempt to serialize an object with a
+     * class that does not implement XmlSerializable.
+     *
+     * Instead it will look at this classmap to see if there is a custom
+     * serializer here. This is useful if you don't want your value objects
+     * to be responsible for serializing themselves.
+     *
+     * The keys in this classmap need to be fully qualified PHP class names,
+     * the values must be callbacks. The callbacks take two arguments. The
+     * writer class, and the value that must be written.
+     *
+     * function (Writer $writer, object $value)
+     *
+     * @var array
+     */
+    public $classMap = [];
+
+    /**
+     * Backups of previous contexts.
+     *
+     * @var array
+     */
+    protected $contextStack = [];
+
+    /**
+     * Create a new "context".
+     *
+     * This allows you to safely modify the elementMap, contextUri or
+     * namespaceMap. After you're done, you can restore the old data again
+     * with popContext.
+     *
+     * @return null
+     */
+    function pushContext() {
+
+        $this->contextStack[] = [
+            $this->elementMap,
+            $this->contextUri,
+            $this->namespaceMap,
+            $this->classMap
+        ];
+
+    }
+
+    /**
+     * Restore the previous "context".
+     *
+     * @return null
+     */
+    function popContext() {
+
+        list(
+            $this->elementMap,
+            $this->contextUri,
+            $this->namespaceMap,
+            $this->classMap
+        ) = array_pop($this->contextStack);
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Deserializer/functions.php b/vendor/sabre/xml/lib/Deserializer/functions.php
new file mode 100644
index 000000000..fe88a6db8
--- /dev/null
+++ b/vendor/sabre/xml/lib/Deserializer/functions.php
@@ -0,0 +1,255 @@
+<?php
+
+namespace Sabre\Xml\Deserializer;
+
+use Sabre\Xml\Reader;
+
+/**
+ * This class provides a number of 'deserializer' helper functions.
+ * These can be used to easily specify custom deserializers for specific
+ * XML elements.
+ *
+ * You can either use these functions from within the $elementMap in the
+ * Service or Reader class, or you can call them from within your own
+ * deserializer functions.
+ */
+
+/*
+ * The 'keyValue' deserializer parses all child elements, and outputs them as
+ * a "key=>value" array.
+ *
+ * For example, keyvalue will parse:
+ *
+ * <?xml version="1.0"?>
+ * <s:root xmlns:s="http://sabredav.org/ns">
+ *   <s:elem1>value1</s:elem1>
+ *   <s:elem2>value2</s:elem2>
+ *   <s:elem3 />
+ * </s:root>
+ *
+ * Into:
+ *
+ * [
+ *   "{http://sabredav.org/ns}elem1" => "value1",
+ *   "{http://sabredav.org/ns}elem2" => "value2",
+ *   "{http://sabredav.org/ns}elem3" => null,
+ * ];
+ *
+ * If you specify the 'namespace' argument, the deserializer will remove
+ * the namespaces of the keys that match that namespace.
+ *
+ * For example, if you call keyValue like this:
+ *
+ * keyValue($reader, 'http://sabredav.org/ns')
+ *
+ * it's output will instead be:
+ *
+ * [
+ *   "elem1" => "value1",
+ *   "elem2" => "value2",
+ *   "elem3" => null,
+ * ];
+ *
+ * Attributes will be removed from the top-level elements. If elements with
+ * the same name appear twice in the list, only the last one will be kept.
+ *
+ *
+ * @param Reader $reader
+ * @param string $namespace
+ * @return array
+ */
+function keyValue(Reader $reader, $namespace = null) {
+
+    // If there's no children, we don't do anything.
+    if ($reader->isEmptyElement) {
+        $reader->next();
+        return [];
+    }
+
+    $values = [];
+
+    $reader->read();
+    do {
+
+        if ($reader->nodeType === Reader::ELEMENT) {
+            if ($namespace !== null && $reader->namespaceURI === $namespace) {
+                $values[$reader->localName] = $reader->parseCurrentElement()['value'];
+            } else {
+                $clark = $reader->getClark();
+                $values[$clark] = $reader->parseCurrentElement()['value'];
+            }
+        } else {
+            $reader->read();
+        }
+    } while ($reader->nodeType !== Reader::END_ELEMENT);
+
+    $reader->read();
+
+    return $values;
+
+}
+
+/**
+ * The 'enum' deserializer parses elements into a simple list
+ * without values or attributes.
+ *
+ * For example, Elements will parse:
+ *
+ * <?xml version="1.0"? >
+ * <s:root xmlns:s="http://sabredav.org/ns">
+ *   <s:elem1 />
+ *   <s:elem2 />
+ *   <s:elem3 />
+ *   <s:elem4>content</s:elem4>
+ *   <s:elem5 attr="val" />
+ * </s:root>
+ *
+ * Into:
+ *
+ * [
+ *   "{http://sabredav.org/ns}elem1",
+ *   "{http://sabredav.org/ns}elem2",
+ *   "{http://sabredav.org/ns}elem3",
+ *   "{http://sabredav.org/ns}elem4",
+ *   "{http://sabredav.org/ns}elem5",
+ * ];
+ *
+ * This is useful for 'enum'-like structures.
+ *
+ * If the $namespace argument is specified, it will strip the namespace
+ * for all elements that match that.
+ *
+ * For example,
+ *
+ * enum($reader, 'http://sabredav.org/ns')
+ *
+ * would return:
+ *
+ * [
+ *   "elem1",
+ *   "elem2",
+ *   "elem3",
+ *   "elem4",
+ *   "elem5",
+ * ];
+ *
+ * @param Reader $reader
+ * @param string $namespace
+ * @return string[]
+ */
+function enum(Reader $reader, $namespace = null) {
+
+    // If there's no children, we don't do anything.
+    if ($reader->isEmptyElement) {
+        $reader->next();
+        return [];
+    }
+    $reader->read();
+    $currentDepth = $reader->depth;
+
+    $values = [];
+    do {
+
+        if ($reader->nodeType !== Reader::ELEMENT) {
+            continue;
+        }
+        if (!is_null($namespace) && $namespace === $reader->namespaceURI) {
+            $values[] = $reader->localName;
+        } else {
+            $values[] = $reader->getClark();
+        }
+
+    } while ($reader->depth >= $currentDepth && $reader->next());
+
+    $reader->next();
+    return $values;
+
+}
+
+/**
+ * The valueObject deserializer turns an xml element into a PHP object of
+ * a specific class.
+ *
+ * This is primarily used by the mapValueObject function from the Service
+ * class, but it can also easily be used for more specific situations.
+ *
+ * @param Reader $reader
+ * @param string $className
+ * @param string $namespace
+ * @return object
+ */
+function valueObject(Reader $reader, $className, $namespace) {
+
+    $valueObject = new $className();
+    if ($reader->isEmptyElement) {
+        $reader->next();
+        return $valueObject;
+    }
+
+    $defaultProperties = get_class_vars($className);
+
+    $reader->read();
+    do {
+
+        if ($reader->nodeType === Reader::ELEMENT && $reader->namespaceURI == $namespace) {
+
+            if (property_exists($valueObject, $reader->localName)) {
+                if (is_array($defaultProperties[$reader->localName])) {
+                    $valueObject->{$reader->localName}[] = $reader->parseCurrentElement()['value'];
+                } else {
+                    $valueObject->{$reader->localName} = $reader->parseCurrentElement()['value'];
+                }
+            } else {
+                // Ignore property
+                $reader->next();
+            }
+        } else {
+            $reader->read();
+        }
+    } while ($reader->nodeType !== Reader::END_ELEMENT);
+
+    $reader->read();
+    return $valueObject;
+
+}
+
+/*
+ * This deserializer helps you deserialize xml structures that look like
+ * this:
+ *
+ * <collection>
+ *    <item>...</item>
+ *    <item>...</item>
+ *    <item>...</item>
+ * </collection>
+ *
+ * Many XML documents use  patterns like that, and this deserializer
+ * allow you to get all the 'items' as an array.
+ *
+ * In that previous example, you would register the deserializer as such:
+ *
+ * $reader->elementMap['{}collection'] = function($reader) {
+ *     return repeatingElements($reader, '{}item');
+ * }
+ *
+ * The repeatingElements deserializer simply returns everything as an array.
+ *
+ * @param Reader $reader
+ * @param string $childElementName Element name in clark-notation
+ * @return array
+ */
+function repeatingElements(Reader $reader, $childElementName) {
+
+    $result = [];
+
+    foreach ($reader->parseGetElements() as $element) {
+
+        if ($element['name'] === $childElementName) {
+            $result[] = $element['value'];
+        }
+
+    }
+
+    return $result;
+
+}
diff --git a/vendor/sabre/xml/lib/Element.php b/vendor/sabre/xml/lib/Element.php
new file mode 100644
index 000000000..dd89c5888
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Sabre\Xml;
+
+/**
+ * This is the XML element interface.
+ *
+ * Elements are responsible for serializing and deserializing part of an XML
+ * document into PHP values.
+ *
+ * It combines XmlSerializable and XmlDeserializable into one logical class
+ * that does both.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface Element extends XmlSerializable, XmlDeserializable {
+
+}
diff --git a/vendor/sabre/xml/lib/Element/Base.php b/vendor/sabre/xml/lib/Element/Base.php
new file mode 100644
index 000000000..f59ba49a0
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element/Base.php
@@ -0,0 +1,91 @@
+<?php
+
+namespace Sabre\Xml\Element;
+
+use Sabre\Xml;
+
+/**
+ * The Base XML element is the standard parser & generator that's used by the
+ * XML reader and writer.
+ *
+ * It spits out a simple PHP array structure during deserialization, that can
+ * also be directly injected back into Writer::write.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Base implements Xml\Element {
+
+    /**
+     * PHP value to serialize.
+     *
+     * @var mixed
+     */
+    protected $value;
+
+    /**
+     * Constructor
+     *
+     * @param mixed $value
+     */
+    function __construct($value = null) {
+
+        $this->value = $value;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializable should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Xml\Writer $writer) {
+
+        $writer->write($this->value);
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * Important note 2: You are responsible for advancing the reader to the
+     * next element. Not doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Xml\Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Xml\Reader $reader) {
+
+        $subTree = $reader->parseInnerTree();
+        return $subTree;
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Element/Cdata.php b/vendor/sabre/xml/lib/Element/Cdata.php
new file mode 100644
index 000000000..5f42c4c6e
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element/Cdata.php
@@ -0,0 +1,64 @@
+<?php
+
+namespace Sabre\Xml\Element;
+
+use Sabre\Xml;
+
+/**
+ * CDATA element.
+ *
+ * This element allows you to easily inject CDATA.
+ *
+ * Note that we strongly recommend avoiding CDATA nodes, unless you definitely
+ * know what you're doing, or you're working with unchangable systems that
+ * require CDATA.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Cdata implements Xml\XmlSerializable
+{
+    /**
+     * CDATA element value.
+     *
+     * @var string
+     */
+    protected $value;
+
+    /**
+     * Constructor
+     *
+     * @param string $value
+     */
+    function __construct($value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Xml\Writer $writer) {
+
+        $writer->writeCData($this->value);
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Element/Elements.php b/vendor/sabre/xml/lib/Element/Elements.php
new file mode 100644
index 000000000..9eefd1bf8
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element/Elements.php
@@ -0,0 +1,108 @@
+<?php
+
+namespace Sabre\Xml\Element;
+
+use Sabre\Xml;
+use Sabre\Xml\Deserializer;
+use Sabre\Xml\Serializer;
+
+/**
+ * 'Elements' is a simple list of elements, without values or attributes.
+ * For example, Elements will parse:
+ *
+ * <?xml version="1.0"?>
+ * <s:root xmlns:s="http://sabredav.org/ns">
+ *   <s:elem1 />
+ *   <s:elem2 />
+ *   <s:elem3 />
+ *   <s:elem4>content</s:elem4>
+ *   <s:elem5 attr="val" />
+ * </s:root>
+ *
+ * Into:
+ *
+ * [
+ *   "{http://sabredav.org/ns}elem1",
+ *   "{http://sabredav.org/ns}elem2",
+ *   "{http://sabredav.org/ns}elem3",
+ *   "{http://sabredav.org/ns}elem4",
+ *   "{http://sabredav.org/ns}elem5",
+ * ];
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Elements implements Xml\Element {
+
+    /**
+     * Value to serialize
+     *
+     * @var array
+     */
+    protected $value;
+
+    /**
+     * Constructor
+     *
+     * @param array $value
+     */
+    function __construct(array $value = []) {
+
+        $this->value = $value;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Xml\Writer $writer) {
+
+        Serializer\enum($writer, $this->value);
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * Important note 2: You are responsible for advancing the reader to the
+     * next element. Not doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseSubTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Xml\Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Xml\Reader $reader) {
+
+        return Deserializer\enum($reader);
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Element/KeyValue.php b/vendor/sabre/xml/lib/Element/KeyValue.php
new file mode 100644
index 000000000..7ce53bf4c
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element/KeyValue.php
@@ -0,0 +1,108 @@
+<?php
+
+namespace Sabre\Xml\Element;
+
+use Sabre\Xml;
+use Sabre\Xml\Deserializer;
+
+/**
+ * 'KeyValue' parses out all child elements from a single node, and outputs a
+ * key=>value struct.
+ *
+ * Attributes will be removed, and duplicate child elements are discarded.
+ * Complex values within the elements will be parsed by the 'standard' parser.
+ *
+ * For example, KeyValue will parse:
+ *
+ * <?xml version="1.0"?>
+ * <s:root xmlns:s="http://sabredav.org/ns">
+ *   <s:elem1>value1</s:elem1>
+ *   <s:elem2>value2</s:elem2>
+ *   <s:elem3 />
+ * </s:root>
+ *
+ * Into:
+ *
+ * [
+ *   "{http://sabredav.org/ns}elem1" => "value1",
+ *   "{http://sabredav.org/ns}elem2" => "value2",
+ *   "{http://sabredav.org/ns}elem3" => null,
+ * ];
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class KeyValue implements Xml\Element {
+
+    /**
+     * Value to serialize
+     *
+     * @var array
+     */
+    protected $value;
+
+    /**
+     * Constructor
+     *
+     * @param array $value
+     */
+    function __construct(array $value = []) {
+
+        $this->value = $value;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Xml\Writer $writer) {
+
+        $writer->write($this->value);
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called staticly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * Important note 2: You are responsible for advancing the reader to the
+     * next element. Not doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Xml\Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Xml\Reader $reader) {
+
+        return Deserializer\keyValue($reader);
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Element/Uri.php b/vendor/sabre/xml/lib/Element/Uri.php
new file mode 100644
index 000000000..8f45c0027
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element/Uri.php
@@ -0,0 +1,104 @@
+<?php
+
+namespace Sabre\Xml\Element;
+
+use Sabre\Xml;
+
+/**
+ * Uri element.
+ *
+ * This represents a single uri. An example of how this may be encoded:
+ *
+ *    <link>/foo/bar</link>
+ *    <d:href xmlns:d="DAV:">http://example.org/hi</d:href>
+ *
+ * If the uri is relative, it will be automatically expanded to an absolute
+ * url during writing and reading, if the contextUri property is set on the
+ * reader and/or writer.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Uri implements Xml\Element {
+
+    /**
+     * Uri element value.
+     *
+     * @var string
+     */
+    protected $value;
+
+    /**
+     * Constructor
+     *
+     * @param string $value
+     */
+    function __construct($value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Xml\Writer $writer) {
+
+        $writer->text(
+            \Sabre\Uri\resolve(
+                $writer->contextUri,
+                $this->value
+            )
+        );
+
+    }
+
+    /**
+     * This method is called during xml parsing.
+     *
+     * This method is called statically, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * Important note 2: You are responsible for advancing the reader to the
+     * next element. Not doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseSubTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Xml\Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Xml\Reader $reader) {
+
+        return new self(
+            \Sabre\Uri\resolve(
+                $reader->contextUri,
+                $reader->readText()
+            )
+        );
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Element/XmlFragment.php b/vendor/sabre/xml/lib/Element/XmlFragment.php
new file mode 100644
index 000000000..0abfac132
--- /dev/null
+++ b/vendor/sabre/xml/lib/Element/XmlFragment.php
@@ -0,0 +1,147 @@
+<?php
+
+namespace Sabre\Xml\Element;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\Writer;
+use Sabre\Xml\Element;
+
+/**
+ * The XmlFragment element allows you to extract a portion of your xml tree,
+ * and get a well-formed xml string.
+ *
+ * This goes a bit beyond `innerXml` and friends, as we'll also match all the
+ * correct namespaces.
+ *
+ * Please note that the XML fragment:
+ *
+ * 1. Will not have an <?xml declaration.
+ * 2. Or a DTD
+ * 3. It will have all the relevant xmlns attributes.
+ * 4. It may not have a root element.
+ */
+class XmlFragment implements Element {
+
+    protected $xml;
+
+    function __construct($xml) {
+
+        $this->xml = $xml;
+
+    }
+
+    function getXml() {
+
+        return $this->xml;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        $reader = new Reader();
+
+        // Wrapping the xml in a container, so root-less values can still be
+        // parsed.
+        $xml = <<<XML
+<?xml version="1.0"?>
+<xml-fragment xmlns="http://sabre.io/ns">{$this->getXml()}</xml-fragment>
+XML;
+
+        $reader->xml($xml);
+
+        while ($reader->read()) {
+
+            if ($reader->depth < 1) {
+                // Skipping the root node.
+                continue;
+            }
+
+            switch ($reader->nodeType) {
+
+                case Reader::ELEMENT :
+                    $writer->startElement(
+                        $reader->getClark()
+                    );
+                    $empty = $reader->isEmptyElement;
+                    while ($reader->moveToNextAttribute()) {
+                        switch ($reader->namespaceURI) {
+                            case '' :
+                                $writer->writeAttribute($reader->localName, $reader->value);
+                                break;
+                            case 'http://www.w3.org/2000/xmlns/' :
+                                // Skip namespace declarations
+                                break;
+                            default :
+                                $writer->writeAttribute($reader->getClark(), $reader->value);
+                                break;
+                        }
+                    }
+                    if ($empty) {
+                        $writer->endElement();
+                    }
+                    break;
+                case Reader::CDATA :
+                case Reader::TEXT :
+                    $writer->text(
+                        $reader->value
+                    );
+                    break;
+                case Reader::END_ELEMENT :
+                    $writer->endElement();
+                    break;
+
+            }
+
+        }
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $result = new self($reader->readInnerXml());
+        $reader->next();
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/LibXMLException.php b/vendor/sabre/xml/lib/LibXMLException.php
new file mode 100644
index 000000000..f0190eb51
--- /dev/null
+++ b/vendor/sabre/xml/lib/LibXMLException.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace Sabre\Xml;
+
+use
+    LibXMLError;
+
+/**
+ * This exception is thrown when the Readers runs into a parsing error.
+ *
+ * This exception effectively wraps 1 or more LibXMLError objects.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class LibXMLException extends ParseException {
+
+    /**
+     * The error list.
+     *
+     * @var LibXMLError[]
+     */
+    protected $errors;
+
+    /**
+     * Creates the exception.
+     *
+     * You should pass a list of LibXMLError objects in its constructor.
+     *
+     * @param LibXMLError[] $errors
+     * @param int $code
+     * @param Exception $previousException
+     */
+    function __construct(array $errors, $code = null, Exception $previousException = null) {
+
+        $this->errors = $errors;
+        parent::__construct($errors[0]->message . ' on line ' . $errors[0]->line . ', column ' . $errors[0]->column, $code, $previousException);
+
+    }
+
+    /**
+     * Returns the LibXML errors
+     *
+     * @return void
+     */
+    function getErrors() {
+
+        return $this->errors;
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/ParseException.php b/vendor/sabre/xml/lib/ParseException.php
new file mode 100644
index 000000000..3a6883b2f
--- /dev/null
+++ b/vendor/sabre/xml/lib/ParseException.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Sabre\Xml;
+
+use
+    Exception;
+
+/**
+ * This is a base exception for any exception related to parsing xml files.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ParseException extends Exception {
+
+}
diff --git a/vendor/sabre/xml/lib/Reader.php b/vendor/sabre/xml/lib/Reader.php
new file mode 100644
index 000000000..7cba76c59
--- /dev/null
+++ b/vendor/sabre/xml/lib/Reader.php
@@ -0,0 +1,308 @@
+<?php
+
+namespace Sabre\Xml;
+
+use XMLReader;
+
+/**
+ * The Reader class expands upon PHP's built-in XMLReader.
+ *
+ * The intended usage, is to assign certain XML elements to PHP classes. These
+ * need to be registered using the $elementMap public property.
+ *
+ * After this is done, a single call to parse() will parse the entire document,
+ * and delegate sub-sections of the document to element classes.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Reader extends XMLReader {
+
+    use ContextStackTrait;
+
+    /**
+     * Returns the current nodename in clark-notation.
+     *
+     * For example: "{http://www.w3.org/2005/Atom}feed".
+     * Or if no namespace is defined: "{}feed".
+     *
+     * This method returns null if we're not currently on an element.
+     *
+     * @return string|null
+     */
+    function getClark() {
+
+        if (! $this->localName) {
+            return null;
+        }
+
+        return '{' . $this->namespaceURI . '}' . $this->localName;
+
+    }
+
+    /**
+     * Reads the entire document.
+     *
+     * This function returns an array with the following three elements:
+     *    * name - The root element name.
+     *    * value - The value for the root element.
+     *    * attributes - An array of attributes.
+     *
+     * This function will also disable the standard libxml error handler (which
+     * usually just results in PHP errors), and throw exceptions instead.
+     *
+     * @return array
+     */
+    function parse() {
+
+        $previousEntityState = libxml_disable_entity_loader(true);
+        $previousSetting = libxml_use_internal_errors(true);
+
+        // Really sorry about the silence operator, seems like I have no
+        // choice. See:
+        //
+        // https://bugs.php.net/bug.php?id=64230
+        while ($this->nodeType !== self::ELEMENT && @$this->read()) {
+            // noop
+        }
+        $result = $this->parseCurrentElement();
+
+        $errors = libxml_get_errors();
+        libxml_clear_errors();
+        libxml_use_internal_errors($previousSetting);
+        libxml_disable_entity_loader($previousEntityState);
+
+        if ($errors) {
+            throw new LibXMLException($errors);
+        }
+
+        return $result;
+    }
+
+
+
+    /**
+     * parseGetElements parses everything in the current sub-tree,
+     * and returns a an array of elements.
+     *
+     * Each element has a 'name', 'value' and 'attributes' key.
+     *
+     * If the the element didn't contain sub-elements, an empty array is always
+     * returned. If there was any text inside the element, it will be
+     * discarded.
+     *
+     * If the $elementMap argument is specified, the existing elementMap will
+     * be overridden while parsing the tree, and restored after this process.
+     *
+     * @param array $elementMap
+     * @return array
+     */
+    function parseGetElements(array $elementMap = null) {
+
+        $result = $this->parseInnerTree($elementMap);
+        if (!is_array($result)) {
+            return [];
+        }
+        return $result;
+
+    }
+
+    /**
+     * Parses all elements below the current element.
+     *
+     * This method will return a string if this was a text-node, or an array if
+     * there were sub-elements.
+     *
+     * If there's both text and sub-elements, the text will be discarded.
+     *
+     * If the $elementMap argument is specified, the existing elementMap will
+     * be overridden while parsing the tree, and restored after this process.
+     *
+     * @param array $elementMap
+     * @return array|string
+     */
+    function parseInnerTree(array $elementMap = null) {
+
+        $text = null;
+        $elements = [];
+
+        if ($this->nodeType === self::ELEMENT && $this->isEmptyElement) {
+            // Easy!
+            $this->next();
+            return null;
+        }
+
+        if (!is_null($elementMap)) {
+            $this->pushContext();
+            $this->elementMap = $elementMap;
+        }
+
+        // Really sorry about the silence operator, seems like I have no
+        // choice. See:
+        //
+        // https://bugs.php.net/bug.php?id=64230
+        if (!@$this->read()) return false;
+
+        while (true) {
+
+            if (!$this->isValid()) {
+
+                $errors = libxml_get_errors();
+
+                if ($errors) {
+                    libxml_clear_errors();
+                    throw new LibXMLException($errors);
+                }
+            }
+
+            switch ($this->nodeType) {
+                case self::ELEMENT :
+                    $elements[] = $this->parseCurrentElement();
+                    break;
+                case self::TEXT :
+                case self::CDATA :
+                    $text .= $this->value;
+                    $this->read();
+                    break;
+                case self::END_ELEMENT :
+                    // Ensuring we are moving the cursor after the end element.
+                    $this->read();
+                    break 2;
+                case self::NONE :
+                    throw new ParseException('We hit the end of the document prematurely. This likely means that some parser "eats" too many elements. Do not attempt to continue parsing.');
+                default :
+                    // Advance to the next element
+                    $this->read();
+                    break;
+            }
+
+        }
+
+        if (!is_null($elementMap)) {
+            $this->popContext();
+        }
+        return ($elements ? $elements : $text);
+
+    }
+
+    /**
+     * Reads all text below the current element, and returns this as a string.
+     *
+     * @return string
+     */
+    function readText() {
+
+        $result = '';
+        $previousDepth = $this->depth;
+
+        while ($this->read() && $this->depth != $previousDepth) {
+            if (in_array($this->nodeType, [XMLReader::TEXT, XMLReader::CDATA, XMLReader::WHITESPACE])) {
+                $result .= $this->value;
+            }
+        }
+        return $result;
+
+    }
+
+    /**
+     * Parses the current XML element.
+     *
+     * This method returns arn array with 3 properties:
+     *   * name - A clark-notation XML element name.
+     *   * value - The parsed value.
+     *   * attributes - A key-value list of attributes.
+     *
+     * @return array
+     */
+    function parseCurrentElement() {
+
+        $name = $this->getClark();
+
+        $attributes = [];
+
+        if ($this->hasAttributes) {
+            $attributes = $this->parseAttributes();
+        }
+
+        $value = call_user_func(
+            $this->getDeserializerForElementName($name),
+            $this
+        );
+
+        return [
+            'name'       => $name,
+            'value'      => $value,
+            'attributes' => $attributes,
+        ];
+    }
+
+
+    /**
+     * Grabs all the attributes from the current element, and returns them as a
+     * key-value array.
+     *
+     * If the attributes are part of the same namespace, they will simply be
+     * short keys. If they are defined on a different namespace, the attribute
+     * name will be retured in clark-notation.
+     *
+     * @return array
+     */
+    function parseAttributes() {
+
+        $attributes = [];
+
+        while ($this->moveToNextAttribute()) {
+            if ($this->namespaceURI) {
+
+                // Ignoring 'xmlns', it doesn't make any sense.
+                if ($this->namespaceURI === 'http://www.w3.org/2000/xmlns/') {
+                    continue;
+                }
+
+                $name = $this->getClark();
+                $attributes[$name] = $this->value;
+
+            } else {
+                $attributes[$this->localName] = $this->value;
+            }
+        }
+        $this->moveToElement();
+
+        return $attributes;
+
+    }
+
+    /**
+     * Returns the function that should be used to parse the element identified
+     * by it's clark-notation name.
+     *
+     * @param string $name
+     * @return callable
+     */
+    function getDeserializerForElementName($name) {
+
+        if (!array_key_exists($name, $this->elementMap)) {
+            return ['Sabre\\Xml\\Element\\Base', 'xmlDeserialize'];
+        }
+
+        $deserializer = $this->elementMap[$name];
+        if (is_subclass_of($deserializer, 'Sabre\\Xml\\XmlDeserializable')) {
+            return [ $deserializer, 'xmlDeserialize' ];
+        }
+
+        if (is_callable($deserializer)) {
+            return $deserializer;
+        }
+
+        $type = gettype($deserializer);
+        if ($type === 'string') {
+            $type .= ' (' . $deserializer . ')';
+        } elseif ($type === 'object') {
+            $type .= ' (' . get_class($deserializer) . ')';
+        }
+        throw new \LogicException('Could not use this type as a deserializer: ' . $type . ' for element: ' . $name);
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Serializer/functions.php b/vendor/sabre/xml/lib/Serializer/functions.php
new file mode 100644
index 000000000..21448017d
--- /dev/null
+++ b/vendor/sabre/xml/lib/Serializer/functions.php
@@ -0,0 +1,249 @@
+<?php
+
+namespace Sabre\Xml\Serializer;
+
+use InvalidArgumentException;
+use Sabre\Xml\Writer;
+use Sabre\Xml\XmlSerializable;
+
+/**
+ * This file provides a number of 'serializer' helper functions.
+ *
+ * These helper functions can be used to easily xml-encode common PHP
+ * data structures, or can be placed in the $classMap.
+ */
+
+/**
+ * The 'enum' serializer writes simple list of elements.
+ *
+ * For example, calling:
+ *
+ * enum($writer, [
+ *   "{http://sabredav.org/ns}elem1",
+ *   "{http://sabredav.org/ns}elem2",
+ *   "{http://sabredav.org/ns}elem3",
+ *   "{http://sabredav.org/ns}elem4",
+ *   "{http://sabredav.org/ns}elem5",
+ * ]);
+ *
+ * Will generate something like this (if the correct namespace is declared):
+ *
+ * <s:elem1 />
+ * <s:elem2 />
+ * <s:elem3 />
+ * <s:elem4>content</s:elem4>
+ * <s:elem5 attr="val" />
+ *
+ * @param Writer $writer
+ * @param string[] $values
+ * @return void
+ */
+function enum(Writer $writer, array $values) {
+
+    foreach ($values as $value) {
+        $writer->writeElement($value);
+    }
+}
+
+/**
+ * The valueObject serializer turns a simple PHP object into a classname.
+ *
+ * Every public property will be encoded as an xml element with the same
+ * name, in the XML namespace as specified.
+ *
+ * Values that are set to null or an empty array are not serialized. To
+ * serialize empty properties, you must specify them as an empty string.
+ *
+ * @param Writer $writer
+ * @param object $valueObject
+ * @param string $namespace
+ */
+function valueObject(Writer $writer, $valueObject, $namespace) {
+    foreach (get_object_vars($valueObject) as $key => $val) {
+        if (is_array($val)) {
+            // If $val is an array, it has a special meaning. We need to
+            // generate one child element for each item in $val
+            foreach ($val as $child) {
+                $writer->writeElement('{' . $namespace . '}' . $key, $child);
+            }
+
+        } elseif ($val !== null) {
+            $writer->writeElement('{' . $namespace . '}' . $key, $val);
+        }
+    }
+}
+
+
+/**
+ * This serializer helps you serialize xml structures that look like
+ * this:
+ *
+ * <collection>
+ *    <item>...</item>
+ *    <item>...</item>
+ *    <item>...</item>
+ * </collection>
+ *
+ * In that previous example, this serializer just serializes the item element,
+ * and this could be called like this:
+ *
+ * repeatingElements($writer, $items, '{}item');
+ *
+ * @param Writer $writer
+ * @param array $items A list of items sabre/xml can serialize.
+ * @param string $childElementName Element name in clark-notation
+ * @return void
+ */
+function repeatingElements(Writer $writer, array $items, $childElementName) {
+
+    foreach ($items as $item) {
+        $writer->writeElement($childElementName, $item);
+    }
+
+}
+
+/**
+ * This function is the 'default' serializer that is able to serialize most
+ * things, and delegates to other serializers if needed.
+ *
+ * The standardSerializer supports a wide-array of values.
+ *
+ * $value may be a string or integer, it will just write out the string as text.
+ * $value may be an instance of XmlSerializable or Element, in which case it
+ *    calls it's xmlSerialize() method.
+ * $value may be a PHP callback/function/closure, in case we call the callback
+ *    and give it the Writer as an argument.
+ * $value may be a an object, and if it's in the classMap we automatically call
+ *    the correct serializer for it.
+ * $value may be null, in which case we do nothing.
+ *
+ * If $value is an array, the array must look like this:
+ *
+ * [
+ *    [
+ *       'name' => '{namespaceUri}element-name',
+ *       'value' => '...',
+ *       'attributes' => [ 'attName' => 'attValue' ]
+ *    ]
+ *    [,
+ *       'name' => '{namespaceUri}element-name2',
+ *       'value' => '...',
+ *    ]
+ * ]
+ *
+ * This would result in xml like:
+ *
+ * <element-name xmlns="namespaceUri" attName="attValue">
+ *   ...
+ * </element-name>
+ * <element-name2>
+ *   ...
+ * </element-name2>
+ *
+ * The value property may be any value standardSerializer supports, so you can
+ * nest data-structures this way. Both value and attributes are optional.
+ *
+ * Alternatively, you can also specify the array using this syntax:
+ *
+ * [
+ *    [
+ *       '{namespaceUri}element-name' => '...',
+ *       '{namespaceUri}element-name2' => '...',
+ *    ]
+ * ]
+ *
+ * This is excellent for simple key->value structures, and here you can also
+ * specify anything for the value.
+ *
+ * You can even mix the two array syntaxes.
+ *
+ * @param Writer $writer
+ * @param string|int|float|bool|array|object
+ * @return void
+ */
+function standardSerializer(Writer $writer, $value) {
+
+    if (is_scalar($value)) {
+
+        // String, integer, float, boolean
+        $writer->text($value);
+
+    } elseif ($value instanceof XmlSerializable) {
+
+        // XmlSerializable classes or Element classes.
+        $value->xmlSerialize($writer);
+
+    } elseif (is_object($value) && isset($writer->classMap[get_class($value)])) {
+
+        // It's an object which class appears in the classmap.
+        $writer->classMap[get_class($value)]($writer, $value);
+
+    } elseif (is_callable($value)) {
+
+        // A callback
+        $value($writer);
+
+    } elseif (is_null($value)) {
+
+        // nothing!
+
+    } elseif (is_array($value) && array_key_exists('name', $value)) {
+
+        // if the array had a 'name' element, we assume that this array
+        // describes a 'name' and optionally 'attributes' and 'value'.
+
+        $name = $value['name'];
+        $attributes = isset($value['attributes']) ? $value['attributes'] : [];
+        $value = isset($value['value']) ? $value['value'] : null;
+
+        $writer->startElement($name);
+        $writer->writeAttributes($attributes);
+        $writer->write($value);
+        $writer->endElement();
+
+    } elseif (is_array($value)) {
+
+        foreach ($value as $name => $item) {
+
+            if (is_int($name)) {
+
+                // This item has a numeric index. We just loop through the
+                // array and throw it back in the writer.
+                standardSerializer($writer, $item);
+
+            } elseif (is_string($name) && is_array($item) && isset($item['attributes'])) {
+
+                // The key is used for a name, but $item has 'attributes' and
+                // possibly 'value'
+                $writer->startElement($name);
+                $writer->writeAttributes($item['attributes']);
+                if (isset($item['value'])) {
+                    $writer->write($item['value']);
+                }
+                $writer->endElement();
+
+            } elseif (is_string($name)) {
+
+                // This was a plain key-value array.
+                $writer->startElement($name);
+                $writer->write($item);
+                $writer->endElement();
+
+            } else {
+
+                throw new InvalidArgumentException('The writer does not know how to serialize arrays with keys of type: ' . gettype($name));
+
+            }
+        }
+
+    } elseif (is_object($value)) {
+
+        throw new InvalidArgumentException('The writer cannot serialize objects of class: ' . get_class($value));
+
+    } else {
+
+        throw new InvalidArgumentException('The writer cannot serialize values of type: ' . gettype($value));
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/Service.php b/vendor/sabre/xml/lib/Service.php
new file mode 100644
index 000000000..b2603a4c7
--- /dev/null
+++ b/vendor/sabre/xml/lib/Service.php
@@ -0,0 +1,291 @@
+<?php
+
+namespace Sabre\Xml;
+
+/**
+ * XML parsing and writing service.
+ *
+ * You are encouraged to make a instance of this for your application and
+ * potentially extend it, as a central API point for dealing with xml and
+ * configuring the reader and writer.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Service {
+
+    /**
+     * This is the element map. It contains a list of XML elements (in clark
+     * notation) as keys and PHP class names as values.
+     *
+     * The PHP class names must implement Sabre\Xml\Element.
+     *
+     * Values may also be a callable. In that case the function will be called
+     * directly.
+     *
+     * @var array
+     */
+    public $elementMap = [];
+
+    /**
+     * This is a list of namespaces that you want to give default prefixes.
+     *
+     * You must make sure you create this entire list before starting to write.
+     * They should be registered on the root element.
+     *
+     * @var array
+     */
+    public $namespaceMap = [];
+
+    /**
+     * This is a list of custom serializers for specific classes.
+     *
+     * The writer may use this if you attempt to serialize an object with a
+     * class that does not implement XmlSerializable.
+     *
+     * Instead it will look at this classmap to see if there is a custom
+     * serializer here. This is useful if you don't want your value objects
+     * to be responsible for serializing themselves.
+     *
+     * The keys in this classmap need to be fully qualified PHP class names,
+     * the values must be callbacks. The callbacks take two arguments. The
+     * writer class, and the value that must be written.
+     *
+     * function (Writer $writer, object $value)
+     *
+     * @var array
+     */
+    public $classMap = [];
+
+    /**
+     * Returns a fresh XML Reader
+     *
+     * @return Reader
+     */
+    function getReader() {
+
+        $r = new Reader();
+        $r->elementMap = $this->elementMap;
+        return $r;
+
+    }
+
+    /**
+     * Returns a fresh xml writer
+     *
+     * @return Writer
+     */
+    function getWriter() {
+
+        $w = new Writer();
+        $w->namespaceMap = $this->namespaceMap;
+        $w->classMap = $this->classMap;
+        return $w;
+
+    }
+
+    /**
+     * Parses a document in full.
+     *
+     * Input may be specified as a string or readable stream resource.
+     * The returned value is the value of the root document.
+     *
+     * Specifying the $contextUri allows the parser to figure out what the URI
+     * of the document was. This allows relative URIs within the document to be
+     * expanded easily.
+     *
+     * The $rootElementName is specified by reference and will be populated
+     * with the root element name of the document.
+     *
+     * @param string|resource $input
+     * @param string|null $contextUri
+     * @param string|null $rootElementName
+     * @throws ParseException
+     * @return array|object|string
+     */
+    function parse($input, $contextUri = null, &$rootElementName = null) {
+
+        if (is_resource($input)) {
+            // Unfortunately the XMLReader doesn't support streams. When it
+            // does, we can optimize this.
+            $input = stream_get_contents($input);
+        }
+        $r = $this->getReader();
+        $r->contextUri = $contextUri;
+        $r->xml($input);
+
+        $result = $r->parse();
+        $rootElementName = $result['name'];
+        return $result['value'];
+
+    }
+
+    /**
+     * Parses a document in full, and specify what the expected root element
+     * name is.
+     *
+     * This function works similar to parse, but the difference is that the
+     * user can specify what the expected name of the root element should be,
+     * in clark notation.
+     *
+     * This is useful in cases where you expected a specific document to be
+     * passed, and reduces the amount of if statements.
+     *
+     * It's also possible to pass an array of expected rootElements if your
+     * code may expect more than one document type.
+     *
+     * @param string|string[] $rootElementName
+     * @param string|resource $input
+     * @param string|null $contextUri
+     * @return void
+     */
+    function expect($rootElementName, $input, $contextUri = null) {
+
+        if (is_resource($input)) {
+            // Unfortunately the XMLReader doesn't support streams. When it
+            // does, we can optimize this.
+            $input = stream_get_contents($input);
+        }
+        $r = $this->getReader();
+        $r->contextUri = $contextUri;
+        $r->xml($input);
+
+        $result = $r->parse();
+        if (!in_array($result['name'], (array)$rootElementName, true)) {
+            throw new ParseException('Expected ' . implode(' or ', (array)$rootElementName) . ' but received ' . $result['name'] . ' as the root element');
+        }
+        return $result['value'];
+
+    }
+
+    /**
+     * Generates an XML document in one go.
+     *
+     * The $rootElement must be specified in clark notation.
+     * The value must be a string, an array or an object implementing
+     * XmlSerializable. Basically, anything that's supported by the Writer
+     * object.
+     *
+     * $contextUri can be used to specify a sort of 'root' of the PHP application,
+     * in case the xml document is used as a http response.
+     *
+     * This allows an implementor to easily create URI's relative to the root
+     * of the domain.
+     *
+     * @param string $rootElementName
+     * @param string|array|XmlSerializable $value
+     * @param string|null $contextUri
+     */
+    function write($rootElementName, $value, $contextUri = null) {
+
+        $w = $this->getWriter();
+        $w->openMemory();
+        $w->contextUri = $contextUri;
+        $w->setIndent(true);
+        $w->startDocument();
+        $w->writeElement($rootElementName, $value);
+        return $w->outputMemory();
+
+    }
+
+    /**
+     * Map an xml element to a PHP class.
+     *
+     * Calling this function will automatically setup the Reader and Writer
+     * classes to turn a specific XML element to a PHP class.
+     *
+     * For example, given a class such as :
+     *
+     * class Author {
+     *   public $firstName;
+     *   public $lastName;
+     * }
+     *
+     * and an XML element such as:
+     *
+     * <author xmlns="http://example.org/ns">
+     *   <firstName>...</firstName>
+     *   <lastName>...</lastName>
+     * </author>
+     *
+     * These can easily be mapped by calling:
+     *
+     * $service->mapValueObject('{http://example.org}author', 'Author');
+     *
+     * @param string $elementName
+     * @param object $className
+     * @return void
+     */
+    function mapValueObject($elementName, $className) {
+        list($namespace) = self::parseClarkNotation($elementName);
+
+        $this->elementMap[$elementName] = function(Reader $reader) use ($className, $namespace) {
+            return \Sabre\Xml\Deserializer\valueObject($reader, $className, $namespace);
+        };
+        $this->classMap[$className] = function(Writer $writer, $valueObject) use ($namespace) {
+            return \Sabre\Xml\Serializer\valueObject($writer, $valueObject, $namespace);
+        };
+        $this->valueObjectMap[$className] = $elementName;
+    }
+
+    /**
+     * Writes a value object.
+     *
+     * This function largely behaves similar to write(), except that it's
+     * intended specifically to serialize a Value Object into an XML document.
+     *
+     * The ValueObject must have been previously registered using
+     * mapValueObject().
+     *
+     * @param object $object
+     * @param string $contextUri
+     * @return void
+     */
+    function writeValueObject($object, $contextUri = null) {
+
+        if (!isset($this->valueObjectMap[get_class($object)])) {
+            throw new \InvalidArgumentException('"' . get_class($object) . '" is not a registered value object class. Register your class with mapValueObject.');
+        }
+        return $this->write(
+            $this->valueObjectMap[get_class($object)],
+            $object,
+            $contextUri
+        );
+
+    }
+
+    /**
+     * Parses a clark-notation string, and returns the namespace and element
+     * name components.
+     *
+     * If the string was invalid, it will throw an InvalidArgumentException.
+     *
+     * @param string $str
+     * @throws InvalidArgumentException
+     * @return array
+     */
+    static function parseClarkNotation($str) {
+        static $cache = [];
+
+        if (!isset($cache[$str])) {
+
+            if (!preg_match('/^{([^}]*)}(.*)$/', $str, $matches)) {
+                throw new \InvalidArgumentException('\'' . $str . '\' is not a valid clark-notation formatted string');
+            }
+
+            $cache[$str] = [
+                $matches[1],
+                $matches[2]
+            ];
+        }
+
+        return $cache[$str];
+    }
+
+    /**
+     * A list of classes and which XML elements they map to.
+     */
+    protected $valueObjectMap = [];
+
+}
diff --git a/vendor/sabre/xml/lib/Version.php b/vendor/sabre/xml/lib/Version.php
new file mode 100644
index 000000000..f199e7158
--- /dev/null
+++ b/vendor/sabre/xml/lib/Version.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Sabre\Xml;
+
+/**
+ * This class contains the version number for this package.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/
+ */
+class Version {
+
+    /**
+     * Full version number
+     */
+    const VERSION = '1.4.1';
+
+}
diff --git a/vendor/sabre/xml/lib/Writer.php b/vendor/sabre/xml/lib/Writer.php
new file mode 100644
index 000000000..adfbe0cb0
--- /dev/null
+++ b/vendor/sabre/xml/lib/Writer.php
@@ -0,0 +1,266 @@
+<?php
+
+namespace Sabre\Xml;
+
+use XMLWriter;
+
+/**
+ * The XML Writer class.
+ *
+ * This class works exactly as PHP's built-in XMLWriter, with a few additions.
+ *
+ * Namespaces can be registered beforehand, globally. When the first element is
+ * written, namespaces will automatically be declared.
+ *
+ * The writeAttribute, startElement and writeElement can now take a
+ * clark-notation element name (example: {http://www.w3.org/2005/Atom}link).
+ *
+ * If, when writing the namespace is a known one a prefix will automatically be
+ * selected, otherwise a random prefix will be generated.
+ *
+ * Instead of standard string values, the writer can take Element classes (as
+ * defined by this library) to delegate the serialization.
+ *
+ * The write() method can take array structures to quickly write out simple xml
+ * trees.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Writer extends XMLWriter {
+
+    use ContextStackTrait;
+
+    /**
+     * Any namespace that the writer is asked to write, will be added here.
+     *
+     * Any of these elements will get a new namespace definition *every single
+     * time* they are used, but this array allows the writer to make sure that
+     * the prefixes are consistent anyway.
+     *
+     * @var array
+     */
+    protected $adhocNamespaces = [];
+
+    /**
+     * When the first element is written, this flag is set to true.
+     *
+     * This ensures that the namespaces in the namespaces map are only written
+     * once.
+     *
+     * @var bool
+     */
+    protected $namespacesWritten = false;
+
+    /**
+     * Writes a value to the output stream.
+     *
+     * The following values are supported:
+     *   1. Scalar values will be written as-is, as text.
+     *   2. Null values will be skipped (resulting in a short xml tag).
+     *   3. If a value is an instance of an Element class, writing will be
+     *      delegated to the object.
+     *   4. If a value is an array, two formats are supported.
+     *
+     *  Array format 1:
+     *  [
+     *    "{namespace}name1" => "..",
+     *    "{namespace}name2" => "..",
+     *  ]
+     *
+     *  One element will be created for each key in this array. The values of
+     *  this array support any format this method supports (this method is
+     *  called recursively).
+     *
+     *  Array format 2:
+     *
+     *  [
+     *    [
+     *      "name" => "{namespace}name1"
+     *      "value" => "..",
+     *      "attributes" => [
+     *          "attr" => "attribute value",
+     *      ]
+     *    ],
+     *    [
+     *      "name" => "{namespace}name1"
+     *      "value" => "..",
+     *      "attributes" => [
+     *          "attr" => "attribute value",
+     *      ]
+     *    ]
+     * ]
+     *
+     * @param mixed $value
+     * @return void
+     */
+    function write($value) {
+
+        Serializer\standardSerializer($this, $value);
+
+    }
+
+    /**
+     * Opens a new element.
+     *
+     * You can either just use a local elementname, or you can use clark-
+     * notation to start a new element.
+     *
+     * Example:
+     *
+     *     $writer->startElement('{http://www.w3.org/2005/Atom}entry');
+     *
+     * Would result in something like:
+     *
+     *     <entry xmlns="http://w3.org/2005/Atom">
+     *
+     * @param string $name
+     * @return bool
+     */
+    function startElement($name) {
+
+        if ($name[0] === '{') {
+
+            list($namespace, $localName) =
+                Service::parseClarkNotation($name);
+
+            if (array_key_exists($namespace, $this->namespaceMap)) {
+                $result = $this->startElementNS(
+                    $this->namespaceMap[$namespace] === '' ?  null : $this->namespaceMap[$namespace],
+                    $localName,
+                    null
+                );
+            } else {
+
+                // An empty namespace means it's the global namespace. This is
+                // allowed, but it mustn't get a prefix.
+                if ($namespace === "" || $namespace === null) {
+                    $result = $this->startElement($localName);
+                    $this->writeAttribute('xmlns', '');
+                } else {
+                    if (!isset($this->adhocNamespaces[$namespace])) {
+                        $this->adhocNamespaces[$namespace] = 'x' . (count($this->adhocNamespaces) + 1);
+                    }
+                    $result = $this->startElementNS($this->adhocNamespaces[$namespace], $localName, $namespace);
+                }
+            }
+
+        } else {
+            $result = parent::startElement($name);
+        }
+
+        if (!$this->namespacesWritten) {
+
+            foreach ($this->namespaceMap as $namespace => $prefix) {
+                $this->writeAttribute(($prefix ? 'xmlns:' . $prefix : 'xmlns'), $namespace);
+            }
+            $this->namespacesWritten = true;
+
+        }
+
+        return $result;
+
+    }
+
+    /**
+     * Write a full element tag and it's contents.
+     *
+     * This method automatically closes the element as well.
+     *
+     * The element name may be specified in clark-notation.
+     *
+     * Examples:
+     *
+     *    $writer->writeElement('{http://www.w3.org/2005/Atom}author',null);
+     *    becomes:
+     *    <author xmlns="http://www.w3.org/2005" />
+     *
+     *    $writer->writeElement('{http://www.w3.org/2005/Atom}author', [
+     *       '{http://www.w3.org/2005/Atom}name' => 'Evert Pot',
+     *    ]);
+     *    becomes:
+     *    <author xmlns="http://www.w3.org/2005" /><name>Evert Pot</name></author>
+     *
+     * @param string $name
+     * @param string $content
+     * @return bool
+     */
+    function writeElement($name, $content = null) {
+
+        $this->startElement($name);
+        if (!is_null($content)) {
+            $this->write($content);
+        }
+        $this->endElement();
+
+    }
+
+    /**
+     * Writes a list of attributes.
+     *
+     * Attributes are specified as a key->value array.
+     *
+     * The key is an attribute name. If the key is a 'localName', the current
+     * xml namespace is assumed. If it's a 'clark notation key', this namespace
+     * will be used instead.
+     *
+     * @param array $attributes
+     * @return void
+     */
+    function writeAttributes(array $attributes) {
+
+        foreach ($attributes as $name => $value) {
+            $this->writeAttribute($name, $value);
+        }
+
+    }
+
+    /**
+     * Writes a new attribute.
+     *
+     * The name may be specified in clark-notation.
+     *
+     * Returns true when successful.
+     *
+     * @param string $name
+     * @param string $value
+     * @return bool
+     */
+    function writeAttribute($name, $value) {
+
+        if ($name[0] === '{') {
+
+            list(
+                $namespace,
+                $localName
+            ) = Service::parseClarkNotation($name);
+
+            if (array_key_exists($namespace, $this->namespaceMap)) {
+                // It's an attribute with a namespace we know
+                $this->writeAttribute(
+                    $this->namespaceMap[$namespace] . ':' . $localName,
+                    $value
+                );
+            } else {
+
+                // We don't know the namespace, we must add it in-line
+                if (!isset($this->adhocNamespaces[$namespace])) {
+                    $this->adhocNamespaces[$namespace] = 'x' . (count($this->adhocNamespaces) + 1);
+                }
+                $this->writeAttributeNS(
+                    $this->adhocNamespaces[$namespace],
+                    $localName,
+                    $namespace,
+                    $value
+                );
+
+            }
+
+        } else {
+            return parent::writeAttribute($name, $value);
+        }
+
+    }
+
+}
diff --git a/vendor/sabre/xml/lib/XmlDeserializable.php b/vendor/sabre/xml/lib/XmlDeserializable.php
new file mode 100644
index 000000000..fa857e82c
--- /dev/null
+++ b/vendor/sabre/xml/lib/XmlDeserializable.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace Sabre\Xml;
+
+/**
+ * Implementing the XmlDeserializable interface allows you to use a class as a
+ * deserializer for a specific element.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface XmlDeserializable {
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statically, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader);
+
+}
diff --git a/vendor/sabre/xml/lib/XmlSerializable.php b/vendor/sabre/xml/lib/XmlSerializable.php
new file mode 100644
index 000000000..3e2c528b9
--- /dev/null
+++ b/vendor/sabre/xml/lib/XmlSerializable.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Sabre\Xml;
+
+/**
+ * Objects implementing XmlSerializable can control how they are represented in
+ * Xml.
+ *
+ * @copyright Copyright (C) 2009-2015 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface XmlSerializable {
+
+    /**
+     * The xmlSerialize method is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer);
+
+}