Resolve "Allow teachers opening lessons on the same day before they start"

Closes #95

See merge request !83

Save not only week, but year for week-related stuff

See merge request !82

Merge branch '64-make-it-possible-to-take-over-the-data-of-the-first-lesson-for-double-lessons' into 'master'

Resolve "Carry over the data of the first lesson for double (or triple, ...) lessons"

Closes #64

See merge request !79

Merge branch 'master' into 64-make-it-possible-to-take-over-the-data-of-the-first-lesson-for-double-lessons

Makes it possible to use the function in other contexts

Save groups a person is member of when personal notes are created

Closes #89

See merge request !78

Update dependency pytest to v6

See merge request !74

Fix #89 to fully work

Update dependency flake8-isort to v4

See merge request !77

Resolve "Add week select to week view"

Closes #65

See merge request !73

# Conflicts:
#	aleksis/apps/alsijil/views.py

Currently translated at 100.0% (121 of 121 strings)

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

Currently translated at 100.0% (125 of 125 strings)

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

Resolve "Do not allow to add personal notes for cancelled lessons"

Closes #82

See merge request !61

Resolve "Show lesson topic and group in week overview"

Closes #62

See merge request !75

Groups are only shown if the current page doesn't show a group

Resolve "[Full register] Only show personal notes of group members"

Closes #89

See merge request !70