inject create_at for compatibility stack

src/py/flwr/server/compat/driver_client_proxy.py

@@ -132,6 +132,13 @@ def _send_receive_recordset(
                 ttl=DEFAULT_TTL,
             ),
         )
+
+        # This would normally be recorded upon common.Message creation
+        # but this compatibility stack doesn't create Messages,
+        # so we need to inject `created_at` manually (needed for 
+        # taskins validation by server.utils.validator)
+        task_ins.task.created_at = time.time()
+
         push_task_ins_req = driver_pb2.PushTaskInsRequest(  # pylint: disable=E1101
             task_ins_list=[task_ins]
         )

src/py/flwr/server/utils/validator.py

@@ -36,7 +36,7 @@ def validate_task_ins_or_res(tasks_ins_res: Union[TaskIns, TaskRes]) -> List[str
         tasks_ins_res.task.created_at < 1711497600.0
     ):  # unix timestamp of 27 March 2024 00h:00m:00s UTC
         validation_errors.append(
-            "`created_at` must be float that records the unix timestamp "
+            "`created_at` must be a float that records the unix timestamp "
             "in seconds when the message was created."
         )
     if tasks_ins_res.task.delivered_at != "":