Merge branch 'master' into 266-add-statistics-page-for-absences

# Conflicts:
#	aleksis/apps/alsijil/frontend/components/coursebook/absences/AbsenceCreationDialog.vue
#	aleksis/apps/alsijil/frontend/components/coursebook/absences/AbsenceCreationForm.vue
#	aleksis/apps/alsijil/frontend/components/coursebook/absences/AbsenceCreationSummary.vue
#	aleksis/apps/alsijil/frontend/components/coursebook/absences/absenceCreation.graphql
#	aleksis/apps/alsijil/frontend/index.js
#	aleksis/apps/alsijil/frontend/messages/de.json
#	aleksis/apps/alsijil/frontend/messages/en.json
#	aleksis/apps/alsijil/schema/__init__.py
#	aleksis/apps/alsijil/schema/absences.py
#	aleksis/apps/alsijil/schema/personal_note.py