Add start time to observation specs

SAS/TMSS/backend/src/tmss/tmssapp/adapters/l2stationspecs.py

@@ -42,6 +42,10 @@ schema = """
       "type": "number",
       "minimum": 1
     },
+    "start_time": {
+      "type": "string",
+      "format": "date-time"
+    },
     "stop_time": {
       "type": "string",
       "format": "date-time"
@@ -213,6 +217,7 @@ def convert_to_l2stationspecs_dict(subtask: models.Subtask) -> dict:
 
         for antenna_field in antenna_field_mapping[antenna_set][station_type]:
             l2stationspecs = {'observation_id': subtask.id,
+                              'start_time': subtask.scheduled_start_time.isoformat(),
                               'stop_time': subtask.scheduled_stop_time.isoformat(),
                               'antenna_field': antenna_field,
                               'antenna_set': antenna_set_mapping[antenna_set][station_type],