Update to Django 4.2

Some breaking changes, some deprecation, but not much to worry about.

• https://docs.djangoproject.com/en/4.2/releases/4.0/
• https://docs.djangoproject.com/en/4.2/releases/4.1/
• https://docs.djangoproject.com/en/4.2/releases/4.2/

4.2 is planned to be released around April 3rd.