Background

Users consider embedded associations equivalent to fields. As noted in MONGOID-4843, Mongoid tracks changes on fields, but does not track changes on embedded associations.

To get around this, some users use a gem mongoid_relations_dirty_tracking which is a hack to add changes tracking.

Requirement

• Mongoid's "changes" and "changed_attributes" methods should track changes to embedded docs, using a hash structure.
• The changes should be tracked for N-levels of nested embedding.
• mongoid_relations_dirty_tracking should be looked at as a model implementation.
• Tracking on the fields of a doc's referenced relations is not needed.