Resolve "Add health check for dbbackup"

Closes #378

See merge request !495

Translations update from Weblate

See merge request !496

Currently translated at 100.0% (439 of 439 strings)

Translation: AlekSIS/AlekSIS-Core
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis/de/

Resolve "Make Celery non-optional"

Closes #359

See merge request !491

This reverts commit c82be665.

This reverts commit 3bae1a9a.

Retrospectively, there is no reasonto wrap every request in a
transaction of its own. Developer should actively consider isolation
in their code.

This came up while trying to figure out how to delay every Celery task
until commit, finding us monkey-patching amqp, and failing.

Merge branch '359-make-celery-non-optional' of edugit.org:AlekSIS/Official/AlekSIS-Core into 359-make-celery-non-optional

Merge branch '359-make-celery-non-optional' of edugit.org:AlekSIS/official/AlekSIS-Core into 359-make-celery-non-optional

Refactor ProgressRecorder for non-optional Celery usage and add doc strings

See merge request !494

Rewrite dirtyfields with FieldTracker

See merge request !492

Release 2.0a4

See merge request !488