[ADD]Add nulable date end allowed

services/operation_services.py

@@ -578,7 +578,7 @@ class OperationsService(Component):
             "id": {"type": "integer"},
             "name": {"type": "string"},
             "date_start": {"type": "date"},
-            "date_end": {"type": "date"},
+            "date_end": {"type": "date", "nullable": True},
             "distribution_key": {"type": "string", "nullable": True},
             "pmo": {"type": "string"},
             "consumer_nb": {"type": "integer"},