Prepare for Django 5.0

• Check compatibility of libraries
  • python-calendarweek
  • django-any-js
  • django-titofisto
  • django-iconify
  • django-favicon-plus-reloaded
  • django-cleavejs
  • django-cachalot
  • django-celery-beat (https://github.com/celery/django-celery-beat/issues/698)
  • django-haystack (https://github.com/django-haystack/django-haystack/issues/1924, https://github.com/django-haystack/django-haystack/releases/tag/v3.3b1)
• Check for relevant changes in CHANGELOG ( AlekSIS#75)
• Logout allowed only via POST