Clarify delta responses with containment, OnDelete, or referential constraints

If an entity is deleted, related entities will be implicitly deleted if a navigation property specifies <OnDelete Action="Cascade" /> or ContainsTarget="true".

It is not explicitly specified if in this case the service has to include a deleted-entity object for each deleted entity in a delta response, or whether it is sufficient to notify clients of the deletion of the principal entity.

Similarly in the presence of referential constraints added the changed entities already carry the necessary information and the added/deleted link objects are redundant.

The JSON Format design goal of omitting everything from the payload that can be deduced from $metadata would indicate to just notifying the deletion of the principal entity.