Improving the compare_entities functions

Summary

I reviewed the compare_entities function from apiutils and identified some problematic cases (e.g. multi-properties). Corresponding unit tests have been created and the functionality repaired.

This is a preparation for a comprehensive review of the merge_entities function. I think it's a good idea to merge this in a first step as it's probably independent from the review of the merge function.

Focus

This one can probably be reviewed line-by-line. Maybe look for missing test-corner-cases that might be needed. The code for checking the value for equality is still not ideal, but I think a more comprehensive review (also adding the recursive reference checker) should be postponed.

Test Environment

There are unit tests.

Check List for the Author

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• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
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• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

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src/caosdb/apiutils.py

@@ -239,7 +239,7 @@ def compare_entities(old_entity: Entity, new_entity: Entity,
         if isinstance(entity, Property):
             raise NotImplementedError("The function compare_entities does not work for "
                                       "comparing abstract properties.")
-    
+
     olddiff: Dict[str, Any] = {"properties": {}, "parents": []}
     newdiff: Dict[str, Any] = {"properties": {}, "parents": []}
 
@@ -347,7 +347,6 @@ def compare_entities(old_entity: Entity, new_entity: Entity,
                 newdiff["properties"].pop(prop.name)
                 olddiff["properties"].pop(prop.name)
 
-            
     # Check whether there are missing properties in old_entity, additionally
     # check for multi-properties that are currently not supported:
     for prop in new_entity.properties:
@@ -355,7 +354,7 @@ def compare_entities(old_entity: Entity, new_entity: Entity,
         if len(matching) > 1:
             raise NotImplementedError(
                 "Comparison not implemented for multi-properties.")
-        
+
         if len([0 for p in old_entity.properties if p.name == prop.name]) == 0:
             newdiff["properties"][prop.name] = {}