It should (eventually) be possible to see who last edited an annotation

Today discussed with the users: currently, annotations are made on a specific field of a specific record within the context of a particular collection (or research group). This should stay that way, but it should also be possible to see who last edited the annotation and preferably, also when.

To be implemented only after #124.

Read issue #124 first, since this work is explicitly deferred until it is implemented. No files, tests, or entry points are named; trace how annotations retain their field, record, collection, and research-group context, then define how the last editor and preferably edit time are stored and displayed.

Written by the indexing model from the issue text.