`module ActiveStorage`, not `ActiveStorage::Class`

The reasons for this commit are:

- uniformity with the other Rails libraries
- (possibly) behave better with respect to autoloading
- fix the index in the generated documentation

Before this commit, run `rake rdoc` generates this left sidebar
(ActiveStorage entries are indexed twice, both inside and outside the module):

<img width="308" alt="before" src="https://user-images.githubusercontent.com/10076/28939523-7c087dec-7846-11e7-9289-38ed4a2930cd.png">

After this commit, run `rake rdoc` generates this left sidebar:
(ActiveStorage entries are only indexed inside the module):

<img width="303" alt="after" src="https://user-images.githubusercontent.com/10076/28939524-7c090be0-7846-11e7-8ee5-29dfecae548e.png">

1 files changed, 85 insertions, 83 deletions

diff --git a/activestorage/lib/active_storage/service/azure_storage_service.rb b/activestorage/lib/active_storage/service/azure_storage_service.rb
index 527dc57eeb..62b13433fe 100644
--- a/activestorage/lib/active_storage/service/azure_storage_service.rb
+++ b/activestorage/lib/active_storage/service/azure_storage_service.rb
@@ -2,114 +2,116 @@ require "active_support/core_ext/numeric/bytes"
 require "azure/storage"
 require "azure/storage/core/auth/shared_access_signature"
 
-# Wraps the Microsoft Azure Storage Blob Service as a Active Storage service.
-# See `ActiveStorage::Service` for the generic API documentation that applies to all services.
-class ActiveStorage::Service::AzureStorageService < ActiveStorage::Service
-  attr_reader :client, :path, :blobs, :container, :signer
-
-  def initialize(path:, storage_account_name:, storage_access_key:, container:)
-    @client = Azure::Storage::Client.create(storage_account_name: storage_account_name, storage_access_key: storage_access_key)
-    @signer = Azure::Storage::Core::Auth::SharedAccessSignature.new(storage_account_name, storage_access_key)
-    @blobs = client.blob_client
-    @container = container
-    @path = path
-  end
+module ActiveStorage
+  # Wraps the Microsoft Azure Storage Blob Service as a Active Storage service.
+  # See `ActiveStorage::Service` for the generic API documentation that applies to all services.
+  class Service::AzureStorageService < Service
+    attr_reader :client, :path, :blobs, :container, :signer
+
+    def initialize(path:, storage_account_name:, storage_access_key:, container:)
+      @client = Azure::Storage::Client.create(storage_account_name: storage_account_name, storage_access_key: storage_access_key)
+      @signer = Azure::Storage::Core::Auth::SharedAccessSignature.new(storage_account_name, storage_access_key)
+      @blobs = client.blob_client
+      @container = container
+      @path = path
+    end
 
-  def upload(key, io, checksum: nil)
-    instrument :upload, key, checksum: checksum do
-      begin
-        blobs.create_block_blob(container, key, io, content_md5: checksum)
-      rescue Azure::Core::Http::HTTPError => e
-        raise ActiveStorage::IntegrityError
+    def upload(key, io, checksum: nil)
+      instrument :upload, key, checksum: checksum do
+        begin
+          blobs.create_block_blob(container, key, io, content_md5: checksum)
+        rescue Azure::Core::Http::HTTPError => e
+          raise ActiveStorage::IntegrityError
+        end
       end
     end
-  end
 
-  def download(key)
-    if block_given?
-      instrument :streaming_download, key do
-        stream(key, &block)
-      end
-    else
-      instrument :download, key do
-        _, io = blobs.get_blob(container, key)
-        io.force_encoding(Encoding::BINARY)
+    def download(key)
+      if block_given?
+        instrument :streaming_download, key do
+          stream(key, &block)
+        end
+      else
+        instrument :download, key do
+          _, io = blobs.get_blob(container, key)
+          io.force_encoding(Encoding::BINARY)
+        end
       end
     end
-  end
 
-  def delete(key)
-    instrument :delete, key do
-      begin
-        blobs.delete_blob(container, key)
-      rescue Azure::Core::Http::HTTPError
-        false
+    def delete(key)
+      instrument :delete, key do
+        begin
+          blobs.delete_blob(container, key)
+        rescue Azure::Core::Http::HTTPError
+          false
+        end
       end
     end
-  end
 
-  def exist?(key)
-    instrument :exist, key do |payload|
-      answer = blob_for(key).present?
-      payload[:exist] = answer
-      answer
+    def exist?(key)
+      instrument :exist, key do |payload|
+        answer = blob_for(key).present?
+        payload[:exist] = answer
+        answer
+      end
     end
-  end
 
-  def url(key, expires_in:, disposition:, filename:)
-    instrument :url, key do |payload|
-      base_url = url_for(key)
-      generated_url = signer.signed_uri(URI(base_url), false, permissions: "r",
-        expiry: format_expiry(expires_in), content_disposition: "#{disposition}; filename=\"#{filename}\"").to_s
+    def url(key, expires_in:, disposition:, filename:)
+      instrument :url, key do |payload|
+        base_url = url_for(key)
+        generated_url = signer.signed_uri(URI(base_url), false, permissions: "r",
+          expiry: format_expiry(expires_in), content_disposition: "#{disposition}; filename=\"#{filename}\"").to_s
 
-      payload[:url] = generated_url
+        payload[:url] = generated_url
 
-      generated_url
+        generated_url
+      end
     end
-  end
 
-  def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-    instrument :url, key do |payload|
-      base_url = url_for(key)
-      generated_url = signer.signed_uri(URI(base_url), false, permissions: "rw",
-        expiry: format_expiry(expires_in)).to_s
+    def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
+      instrument :url, key do |payload|
+        base_url = url_for(key)
+        generated_url = signer.signed_uri(URI(base_url), false, permissions: "rw",
+          expiry: format_expiry(expires_in)).to_s
 
-      payload[:url] = generated_url
+        payload[:url] = generated_url
 
-      generated_url
+        generated_url
+      end
     end
-  end
-
-  def headers_for_direct_upload(key, content_type:, checksum:, **)
-    { "Content-Type" => content_type, "Content-MD5" => checksum, "x-ms-blob-type" => "BlockBlob" }
-  end
 
-  private
-    def url_for(key)
-      "#{path}/#{container}/#{key}"
+    def headers_for_direct_upload(key, content_type:, checksum:, **)
+      { "Content-Type" => content_type, "Content-MD5" => checksum, "x-ms-blob-type" => "BlockBlob" }
     end
 
-    def blob_for(key)
-      blobs.get_blob_properties(container, key)
-    rescue Azure::Core::Http::HTTPError
-      false
-    end
+    private
+      def url_for(key)
+        "#{path}/#{container}/#{key}"
+      end
 
-    def format_expiry(expires_in)
-      expires_in ? Time.now.utc.advance(seconds: expires_in).iso8601 : nil
-    end
+      def blob_for(key)
+        blobs.get_blob_properties(container, key)
+      rescue Azure::Core::Http::HTTPError
+        false
+      end
+
+      def format_expiry(expires_in)
+        expires_in ? Time.now.utc.advance(seconds: expires_in).iso8601 : nil
+      end
 
-    # Reads the object for the given key in chunks, yielding each to the block.
-    def stream(key, options = {}, &block)
-      blob = blob_for(key)
+      # Reads the object for the given key in chunks, yielding each to the block.
+      def stream(key, options = {}, &block)
+        blob = blob_for(key)
 
-      chunk_size = 5.megabytes
-      offset = 0
+        chunk_size = 5.megabytes
+        offset = 0
 
-      while offset < blob.properties[:content_length]
-        _, io = blobs.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
-        yield io
-        offset += chunk_size
+        while offset < blob.properties[:content_length]
+          _, io = blobs.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
+          yield io
+          offset += chunk_size
+        end
       end
-    end
+  end
 end