Add a public API to allow users to specify column types

As a result of all of the refactoring that's been done, it's now
possible for us to define a public API to allow users to specify
behavior. This is an initial implementation so that I can work off of it
in smaller pieces for additional features/refactorings.

The current behavior will continue to stay the same, though I'd like to
refactor towards the automatic schema detection being built off of this
API, and add the ability to opt out of automatic schema detection.

Use cases:

- We can deprecate a lot of the edge cases around types, now that there
  is an alternate path for users who wish to maintain the same behavior.
- I intend to refactor serialized columns to be built on top of this
  API.
- Gem and library maintainers are able to interact with `ActiveRecord`
  at a slightly lower level in a more stable way.
- Interesting ability to reverse the work flow of adding to the schema.
  Model can become the single source of truth for the structure. We can
  compare that to what the database says the schema is, diff them, and
  generate a migration.

1 files changed, 2 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index db4d5f0129..8b0fffcf06 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -19,6 +19,7 @@ require 'active_record/errors'
 require 'active_record/log_subscriber'
 require 'active_record/explain_subscriber'
 require 'active_record/relation/delegation'
+require 'active_record/properties'
 
 module ActiveRecord #:nodoc:
   # = Active Record
@@ -321,6 +322,7 @@ module ActiveRecord #:nodoc:
     include Reflection
     include Serialization
     include Store
+    include Properties
   end
 
   ActiveSupport.run_load_hooks(:active_record, Base)