F fix merge entity conflicts

Summary

Part of https://gitlab.indiscale.com/caosdb/customers/leibniz-zmt/management/-/issues/125. Adds a new apiutils.empty_diff function to check for the identity of two Entity objects in the sense of no differences between the two entities. It also adds optional arguments to compare_entities and merge_entities to determine whether or not referenced Entity objects will be compared/merged.

Focus

Mainly, new cases to the value comparison of reference properties have been added to the compare_entities function. Note that the compare_referenced_records argument of the compare_entities function defaults False in order to restore the previous behavior. In contrast, the default of merge_references_with_empty_diffs of merge_entities is True because a) the function is Experimental anyway, so breaking previous behavior is ok, and b) in most of the (e.g., crawler) cases this is probably what a merge is expected to do.

Test Environment

Unit tests should be sufficient; but you can also test it with ZMT's Pangaea crawler.

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• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
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unittests/test_apiutils.py

@@ -393,6 +393,21 @@ def test_wrong_merge_conflict_reference():
     assert rec_a.get_property(license_rt.name) is not None
     assert rec_a.get_property(license_rt.name).value is not None
     assert isinstance(rec_a.get_property(license_rt.name).value, db.Record)
+    assert rec_a.get_property(license_rt.name).value.name == license_rec_a.name
+    assert rec_a.get_property(license_rt.name).value.name == license_rec_b.name
+    assert rec_a.get_property("title").value == "Some dataset title"
+    assert rec_a.get_property("doi").value == "https://doi.org/12345.678"
+
+    # this does not compare referenced records, so it will fail
+    with pytest.raises(RuntimeError) as re:
+        merge_entities(rec_a, rec_b, merge_references_with_empty_diffs=False)
+    assert "Merge conflict" in str(re.value)
+
+    # ... as should this, of course
+    rec_b.get_property(license_rt.name).value.name = "Another license"
+    with pytest.raises(RuntimeError) as re:
+        merge_entities(rec_a, rec_b)
+    assert "Merge conflict" in str(re.value)
 
 
 def test_empty_diff():