[update] relax "MUST change type context attribute to indicate incompatible changes" to allow deprecation cycle on property basis

(i) This issue has been manually transferred from a former internal repository, as a private repository issue cannot be transferred to a public repository.

Context

Currently, API providers are enforced to introduce a new event type whenever incompatible changes are made.

The following alternative approach should be allowed too:

1. Add a new property
2. Communicate the planned deprecation with all parties and settle on a sunset date
3. Deprecating the old property with the specific sunset date
4. Removing the old property after sunset date, making sure that no consumer uses the old property beforehand.

The advantage of this approach is that no additional versions need to be maintained. The disadvantage is that one can not use the Galapagos subscription model to verify that no consumer uses an old schema version before sunsetting it.

Start by locating the guideline that requires a new event type for incompatible changes and compare it with the proposed property-level deprecation cycle. Done means the guideline clearly permits the alternative, including communication, a sunset date, and removal after consumers have migrated.