Merge branch '69-go-to-next-week-if-current-day-is-out-of-range-weekly-timetable-view' into 'master'

Resolve "Go to next week if current day is out of range (weekly timetable view)"

Closes #69

See merge request !88

Merge branch '93-show-substitutions-extra-lessons-events-in-which-a-person-is-the-new-teacher-in-my-timetable' into 'master'

Resolve "Show extra lessons in which a person is the new teacher in "My timetable""

Closes #93

See merge request !91

Fix import

See merge request !90

Fix order of date-related mixins for absences, events and extra lessons

See merge request !86

Resolve "Wrong tooltip for rooms in substitution table"

Closes #92

See merge request !87

Update lockfile

See merge request !89

Minimize query count

Closes #79

See merge request !83

Fix substitutions queryset

See merge request !84

Currently translated at 100.0% (113 of 113 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/de/

Currently translated at 0.8% (1 of 113 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/la/

Currently translated at 100.0% (113 of 113 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/de/

Fix date generation in WeekRelatedMixin

See merge request !82

Add property period_choices to TimePeriod with all periods as choices list

See merge request !81

Merge branch '91-link-substitutions-and-other-week-related-stuff-not-only-to-weeks-but-also-to-years' into 'master'

Resolve "Link substitutions and other week-related stuff not only to weeks, but also to years"

Closes #91

See merge request !80

Update dependency pytest to v6

See merge request !75

Update dependency flake8-isort to v4

See merge request !79