TMSS-1003: Update tests for state transitions; update 'unschedulable' state is not an end state anymore

TMSS-850: use database triggers to block updates on blueprint tables for immutable fields. This is a postgres specific solution, but the most reliable one to truly block and forbid immutable fields.

TMSS-850: Test concrete use case where we simulate that an observation ran fine, but a pipeline failed. Then create an exact copy of the pipeline and let that run

TMSS-850: added initial version of test for test_rerun_copy_of_failed_pipeline. ToDo: refactor into generic rerun task method

TMSS-850: renamed create_task_drafts_for_scheduling_unit_draft into update_task_graph_from_specifications_doc and updated docstrings

TMSS-850: added a test to copy the exported specifications_doc from a blueprint back into an altered/wiped draft graph ad reuse it.

TMSS-955: fixed the dependency issues. We need to upload/populate the templates from a client, which means that tmss itself must be up and running (and migrations are done). After that, the taskconnectortypes can be populated. And after that the permissions. The latter needs direct dajngo access, so as a result the tmss_populate program now has both an http rest client and direct djanog access.

TMSS-850: create_task_drafts_for_scheduling_unit_draft now works in one single transaction which either succeeds or rolls back. The entire TaskGraph is compared to the specifications_doc, new TasksDrafts are created, existing ones are updated, and obsolete ones are removed. Tested all scenarios.

TMSS-850: moved SchedulingUnitBlueprintIndirectModificationsTestCase from t_tasks to t_scheduling_units. Implemented rudimentary first test for import/export specifications_doc on draft. Fixed some tests in t_scheduling_units.

TMSS-850: renamed requirements_doc/template to specifications_doc/template to be more in line with the (sub)tasks

TMSS-64: 'pipeline control' -> 'preprocessing pipeline' to distinguish various pipeline subtasks properly. 'pipeline control' refers to a process used by all pipelines, regardless of their specification, as it interfaces with the generated parset instead.

TMSS-501 Create scheduling_units test for testing the flat_station_list of scheduling_unit blueprint. Also move the status testcase from task to scheduling units