Resolve "Allow configuring database options"

Closes #36

See merge request !104

Resolve "Disambiguate long group names"

Closes #35

See merge request !103

Resolve "Delete deleted events"

Closes #34

See merge request !102

Resolve "Replace every occurrence of UNTIS by Untis"

Closes #30

See merge request !101

Resolve "move_dates_for_testing throws misleading errors"

Closes #33

See merge request !100

Add trademark hint to readme

See merge request !99

Update dev dependencies and reformat

See merge request !98

Resolve "Classes without teachers break import"

Closes #32

See merge request !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 !91

Update poetry.lock

See merge request !92

Provide demo data

See merge request !90

Update changelog from 2.0rc3

See merge request !89