Resolve "Check if getters for lesson periods work correctly"

Closes #118

See merge request !141

Unify API of lesson period with event and extra lesson by adding properties for group names

See merge request !139

Extend querysets for holidays and groups

See merge request !138

Resolve "Holiday.in_week works wrong because of variable shadowing"

Closes #115

See merge request !137

Trigger dist pipeline on master

See merge request !136

Update ci config

See merge request !135

Update poetry.lock

See merge request !134

Resolve "TimePeriod.from_period doesn't respect weekdays"

Closes #111

See merge request !133

Merge branch '110-let-next-prev_lesson-return-none-if-the-person-isn-t-a-participant-of-the-lesson' into 'master'

Resolve "Let next/prev_lesson return None if the person isn't a participant of the lesson"

Closes #110

See merge request !132

Rewrite some API on Event and ExtraLesson

See merge request !129

Update poetry.lock

See merge request !131

Resolve "CSS for week timetable and dashboard widget broken"

Closes #109

See merge request !130

Needed in Alsijil etc.

Remove request

See merge request !128

Add template for pull requests at GitHub for mirroring

See merge request !127

Resolve "_adjacent_lesson doesn't respect persons without lessons"

Closes #107

See merge request !126

Fix view of regular plans

See merge request !125