2755 Add ability to extend HostNode, NetworkNode, Service and Application outside PrimAITE.

tests/unit_tests/_primaite/_simulator/_system/_applications/test_application_registry.py

@@ -8,7 +8,7 @@ def test_adding_to_app_registry():
     class temp_application(Application, identifier="temp_app"):
         pass
 
-    assert Application._application_registry["temp_app"] is temp_application
+    assert Application._registry["temp_app"] is temp_application
 
     with pytest.raises(ValueError):
 
@@ -19,4 +19,4 @@ def test_adding_to_app_registry():
     # Because pytest doesn't reimport classes from modules, registering this temporary test application will change the
     # state of the Application registry for all subsequently run tests. So, we have to delete and unregister the class.
     del temp_application
-    Application._application_registry.pop("temp_app")
+    Application._registry.pop("temp_app")