Resolve TMSS-1144

Closes TMSS-1144

See merge request !635

TMSS-1216: we foresee more problems when draft can be NULL, then when we enforce the link to stay which guarentees that we can follow the path_to_project for blueprints

Resolve TMSS-763

Closes TMSS-763

See merge request !637

TMSS-1144: set provenance chain subtasks to finished. Do not alter dataproducts (which is now forbidden), but test on new instances

TMSS-1144: skip non-finished and/or obsolete subtasks, as they are not part of the successfull provenance chain

Resolve TMSS-985

Closes TMSS-985

See merge request !636

TMSS-1124: added missing TaskTemplateExtendedSerializer for specifications_template of TaskDraftExtendedSerializer

TMSS-1124

Closes TMSS-1124

See merge request !633

TMSS-1124: using first is ok according to !633 (comment 24581)

TMSS-1124: create a subtask_output per task_connector_type of the task, but only with role Correlator or Beamformer because that is what observations produce

TMSS-1124: fetch the subtask's input/output dataproducts and all related properties in one queryset. Major speedup