Resolve "Celery tasks are not working properly"

Closes #37

See merge request !108

Do not include non-package files in wheel

See merge request AlekSIS/official/AlekSIS-App-Untis!107

Fix readme reference

See merge request !106

Resolve "Allow configuring database options"

Closes #36

See merge request !104

Resolve "Disambiguate long group names"

Closes #35

See merge request AlekSIS/official/AlekSIS-App-Untis!103

Resolve "Delete deleted events"

Closes #34

See merge request AlekSIS/official/AlekSIS-App-Untis!102

Resolve "Replace every occurrence of UNTIS by Untis"

Closes #30

See merge request AlekSIS/official/AlekSIS-App-Untis!101

Resolve "move_dates_for_testing throws misleading errors"

Closes #33

See merge request AlekSIS/official/AlekSIS-App-Untis!100

Add trademark hint to readme

See merge request AlekSIS/official/AlekSIS-App-Untis!99

Update dev dependencies and reformat

See merge request !98

Resolve "Classes without teachers break import"

Closes #32

See merge request AlekSIS/official/AlekSIS-App-Untis!97

Add makemessages env to tox.ini

See merge request !96

Bump development version to 2.1.dev0

See merge request !95

Update changelog from 2.0

See merge request !94

(cherry picked from commit 69336497)

Resolve "Management commands are not run in the frontend"

Closes #29

See merge request AlekSIS/official/AlekSIS-App-Untis!91

Update poetry.lock

See merge request !92