F merge id with resolved entity

Summary

One half of the fix for caosdb-crawler#113 (closed). Introduces a merge_id_with_resolved_entity parameter to the apiutils.merge_entities function, that allows to identify an id value of a reference property with an entity that has this id.

Focus

Check whether you can find cases that the new unit test doesn't cover.

Test Environment

Unit test should be sufficient, but you can also run the new int test from caosdb-crawler!141 (merged) and verify that this enhancement resolves the bug.

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CHANGELOG.md

@@ -9,6 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added ###
 
+* `apiutils.merge_entities` now has a `merge_id_with_resolved_entity` keyword
+  which allows to identify property values with each other in case that one is
+  an id and the other is an Entity with this id. Default is ``False``, so no
+  change to the default behavior.
+
 ### Changed ###
 
 ### Deprecated ###