Filter tokens with an associated build trigger from the list API. Delete associated tokens when deleting a trigger.

endpoints/api/trigger.py

@@ -81,6 +81,7 @@ class BuildTrigger(RepositoryParamResource):
                   'service': trigger.service.name, 'config': config_dict},
                  repo=model.get_repository(namespace, repository))
 
+    trigger.write_token.delete_instance()
     trigger.delete_instance(recursive=True)
     return 'No Content', 204