DOC: comment for improving recursion detection

src/caosdb/apiutils.py

@@ -300,6 +300,7 @@ def compare_entities(old_entity: Entity, new_entity: Entity, compare_referenced_
                     # scalar reference
                     if isinstance(prop.value, Entity) and isinstance(matching[0].value, Entity):
                         # explicitely not recursive to prevent infinite recursion
+                        # TODO: why not use a recursion detection with a cache?
                         same_value = empty_diff(
                             prop.value, matching[0].value, compare_referenced_records=False)
                     # list of references