When building the :object_changes metadata, use the serialized value for any attributes that are serialized

[TylerRick]

This way, we store the same (serialized) representation of an attribute in object_changes that ActiveRecord itself uses when it stores the attribute value in the model's table.

[TylerRick]

Question: This only handles serialization of attributes. Should we also unserialize each serialized attribute using the serializer, the same way read_attribute_before_type_cast does (attribute_methods/serialization.rb)?

      def read_attribute_before_type_cast(attr_name)
        if serialized_attributes.include?(attr_name)
          super.unserialized_value
        else
          super
        end
      end

I'm starting to think that we should, so that version.changeset returns the original, unserialized value the same as record.changes does before saving the record...

[TylerRick]

Added a commit which adds unserialization to changeset, similar to what attributes_before_type_cast does (#8078).

Now version.changeset returns the same thing that record.changes returned before the save.

[TylerRick]

Note that this issue is not a duplicate of #164. These two pull requests deal with the serialization at different levels and should both be merged in, in my opinion.

#180 takes care of automatically serializing/unserializing any attributes that have a custom serializer defined in the model, while #164 takes care of serializing an updated record's changes hash into the Version#object_changes attribute (which is like adding a custom serializer line to the Version model).