server: fix return_json method return values

server/atheneum/api.py

@@ -30,8 +30,7 @@ def return_json(func: Callable) -> Callable:
         if isinstance(result, Response):
             return result
         if isinstance(result, APIMessage):
-            response = jsonify(result.payload)
-            response.status = result.status
+            return jsonify(result.payload), result.status
         return jsonify(result)
 
     return decorate