L2SS-1269: removed supervisor ini files for TMSS for scu, as we now deploy and run using docker-compose

TMSS-2227: added 'placed' flag to scheduling unit, set it in mid-term scheduler, reset it at start of scheduling. Push it on the websocket.

TMSS-2186: determine websocket update recipients based on object instance and condider project-based permissions

TMSS-1806: added Subsystem and SubsystemStatus models, and use it everywhere to set the scheduler subsystem active/idle and broadcast those events via the bus and websocket

TMSS-556: Add auth token check in WS handleMessage method; update WS tests to send auth token as first message

Master merge

The environment file ended in test and this is confusing when dealing
with test and production environment since it has nothing to do with
test environments. The extention was used to test out thing while
leaving the old .lofar_env file unchanged. But it ended up this way in
production and its changed in code with this commit.

TMSS-1254: after discussion with the architect we opted for collapsing the scheduled_process_start/stop_time and scheduled_sky_start/stop_time into one more meaningful scheduled_start/stop_time. This timestamp specifies what we want. The actual_* timestamps the report what happened. And the plain timestamps report the combination of the two: what we want before running, and what happened after ending. Moved the timestamps also into the model as non-editable fields which are updated via database triggers. Added documentation.

TMSS-917: adapted and fixed various tests now that we reverted to a single parent TaskBlueprint for a Subtask.

TMSS-725: processed review comment. moved set_subtask_state_following_allowed_transitions into test_utils so that it is clearly intended to be used in tests only, and not in normal tmss code. Took the opportunity to move the TMSSTestEnvironment into its own module as well to make a clear distinction between test-helper-methods (in test_utils.py) and the TMSSTestEnvironment (in test_environment.py). Adapted all tests with new import paths.