TMSS-60: as discussed with the architect, removed overdesigned SubtaskConnector

SAS/TMSS/src/tmss/tmssapp/migrations/0001_initial.py

SAS/TMSS/src/tmss/tmssapp/migrations/0002_populate.py

SAS/TMSS/src/tmss/tmssapp/models/scheduling.py

SAS/TMSS/src/tmss/tmssapp/serializers/scheduling.py

SAS/TMSS/src/tmss/tmssapp/viewsets/scheduling.py

SAS/TMSS/src/tmss/urls.py

SAS/TMSS/test/t_tmssapp_scheduling_django_API.py

SAS/TMSS/test/tmss_test_data_django_models.py

SAS/TMSS/test/tmss_test_data_rest.py