MONGOID-5502: Rails framework compatibility docs (#5751)

* MONGOID-5502: Rails framework compatibility docs

* Updated based on PR feedback

* PR feedback updates

* Fix typo

* Add link to Redis adapter

* Fix grammar

* Fix typo

* Fix spacing

* Updates based on PR

* updated

Author: alexbevi

source/includes/unicode-ballot-x.rst

@@ -0,0 +1 @@
+.. |x| unicode:: U+2717

source/reference/compatibility.txt

@@ -541,3 +541,85 @@ are supported by Mongoid.
   8.0 and 8.1 stable branches.
 
 .. include:: /includes/unicode-checkmark.rst
+.. include:: /includes/unicode-ballot-x.rst
+
+Rails Frameworks Support
+------------------------
+
+Ruby on Rails is comprised of a number of frameworks, which Mongoid attempts to
+provide compatibility with wherever possible.
+
+Though Mongoid attempts to offer API compatibility with `Active Record <https://guides.rubyonrails.org/active_record_basics.html>`_,
+libraries that depend directly on Active Record may not work as expected when
+Mongoid is used as a drop-in replacement.
+
+.. note::
+
+  Mongoid can be used alongside Active Record within the same application without issue.
+
+.. list-table::
+   :header-rows: 1
+   :stub-columns: 1
+   :class: compatibility-large no-padding
+
+   * - Rails Framework
+     - Supported?
+
+   * - ``ActionCable``
+     - |checkmark| [#rails-actioncable-dependency]_
+
+   * - ``ActionMailbox``
+     - |x| [#rails-activerecord-dependency]_
+
+   * - ``ActionMailer``
+     - |checkmark|
+
+   * - ``ActionPack``
+     - |checkmark|
+
+   * - ``ActionText``
+     - |x| [#rails-activerecord-dependency]_
+
+   * - ``ActionView``
+     - |checkmark|
+
+   * - ``ActiveJob``
+     - |checkmark| [#rails-activejob-dependency]_
+
+   * - ``ActiveModel``
+     - |checkmark| [#rails-activemodel-dependency]_
+
+   * - ``ActiveStorage``
+     - |x| [#rails-activerecord-dependency]_
+
+   * - ``ActiveSupport``
+     - |checkmark| [#rails-activesupport-dependency]_
+
+.. [#rails-actioncable-dependency] There is currently no MongoDB adapter for
+   ``ActionCable``, however any existing adapter (such as `Redis <https://guides.rubyonrails.org/action_cable_overview.html#redis-adapter>`_)
+   can be used successfully in conjunction with Mongoid models
+
+.. [#rails-activerecord-dependency] Depends directly on ``ActiveRecord``
+
+.. [#rails-activemodel-dependency] ``Mongoid::Document`` includes ``ActiveModel::Model``
+   and leverages ``ActiveModel::Validations`` for validations
+
+.. [#rails-activesupport-dependency] ``Mongoid`` requires ``ActiveSupport`` and
+   uses it extensively, including ``ActiveSupport::TimeWithZone`` for time handling.
+
+
+
+.. [#rails-activejob-dependency] Serialization of BSON & Mongoid objects works best
+   if you explicitly send ``BSON::ObjectId``'s as strings, and reconstitute them in the job:
+
+   .. code-block:: ruby
+
+    record = Model.find(...)
+    MyJob.perform_later(record._id.to_s)
+
+    class MyJob < ApplicationJob
+      def perform(id_as_string)
+        record = Model.find(id_as_string)
+        # ...
+      end
+    end