Container could fail to delete when there were reference properties

Summary

Fix for #179 (closed) and also #180 (closed)

Focus

• Does it work?
• No regressions to expect?

Test Environment

Run unit test: pytest test_container.py, also run integration tests

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• All automated tests pass
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src/linkahead/common/models.py

@@ -3292,7+3292,7 @@
                             for list_item in prop.value:
                                 if isinstance(list_item, int):
                                     is_being_referenced.add(list_item)
                                 else:
                                     is_being_referenced.add(list_item.id)
                         else:
                             try:
@@ -3314,7+3314,7 @@
 
                 if hasattr(prop, 'id'):
                     is_property.add(prop.id)
+            if isinstance(container_item, Property):
+                dtype = container_item.datatype
+                if isinstance(dtype, Entity):
+                    is_being_referenced.add(dtype.id)
+                elif isinstance(dtype, str):
+                    if is_list_datatype(dtype):
+                        dtype = get_list_datatype(dtype)
+                    try:
+                        is_being_referenced.add(container.get_entity_by_name(dtype).id)
+                    except KeyError:
+                        pass
+                else:
+                    # plain old scalar datatype
+                    pass
 
         dependent_parents = item_id.intersection(is_parent)
         dependent_properties = item_id.intersection(is_property)