Hopefully resolve UTC-Event-Timezone-Bug

Upgrade django to 4.1
Upgrade django-timezone-field, django-simple-history, django-debug-toolbar and django-bootstrap-datepicker-plus
Upgrade mysqlclient
Remove obsolete pytz
Adapt timezone handling code to new interface of TimezoneInfo (part of python since 3.9 and backport included in 3.8)
Drop support for python 3.7 (since Django 4 requires >= 3.8)

Add start and end inputs below the calendar widget that can be used to add new entries to the calendar.
Inputs are based on html5 widgets, will fallback to simple text inputs in very old browsers. Modern browsers also provide an integrated validation of the time ranges. In older browsers, this will be done latest on server side.
This implements #124

Benjamin Hättasch authored 2 years ago and Nadja Geisler committed 2 years ago

Manually trigger post_save signal after bulk create of replacing availabilities
This fixes #132

fixes #81

availabilities in AK submission
availabilities in AK wish submission