Merge branch 'L2SS-1197-add-antenna-set' into 'main'

L2SS-1197: add antenna_set entry

Closes L2SS-1197

See merge request !37

tests/observation/test_multi_station_observation.py

@@ -6,23 +6,21 @@
 # See LICENSE.txt for more info.
 
 from unittest import mock
-
-
-from tests import base
+import concurrent.futures
 from json import loads
+from tests import base
 
 from lofar_station_client.observation.multi_station_observation import (
     MultiStationObservation,
 )
 
 
-import concurrent.futures
-
 SPEC_DICT = loads(
     """
         {
           "observation_id": 12345,
           "stop_time": "2106-02-07T00:00:00",
+          "antenna_set": "ALL",
           "antenna_mask": [0,1,2,9],
           "filter": "HBA_110_190",
           "SAPs": [{