Update to Django 4.2

[transistortim]

Django 3.2 will be end of life on 01.04.2024. The new LTS version is Django 4.2.

Django 4.2 has to be supported by all dependencies before we update. See table below for version info.

Dependency	Update required	Remarks
crispy-bootstrap5	yes, to 2023.10	drops Django 3.2 support
django-crispy-forms	no	supported since 2.0
django-extensions	no	supported since 3.2.3
django-impersonate	?	4.0 support added in 1.8.0, we're on 1.9.1
django-password-reset	yes, to 3.0.0	3.0.0 is not on PyPI, we're on 2.0
django-phonenumber-field[phonenumbers]	no	supported since 7.1.0
django-post-office	?	4.0 support added in 3.6.0, we're on 3.7.0
django-select2	no	supported since 8.1.2
django-sendfile2	?	4.0 support since 0.6.1, we're on 0.7.0
django-tables2	no	supported since 2.6.0
fontawesomefree	no	package just contains static data & empty init.py
Pillow	no	not a Django package
psycopg2-binary	no	we should switch to pyscopg-binary sometime (see https://docs.djangoproject.com/en/4.2/ref/databases/#postgresql-notes)
pwgen	no	not a Django package
Sphinx	no	not a Django package
sphinx-rtd-theme	no	not a Django package
uWSGI	no	not a Django package
Xlsxcursor	no	not a Django package
XlsxWriter	no	not a Django package

Concerning our code, we should look into:

• Migrating from pytz to zoneinfo, see https://docs.djangoproject.com/en/5.0/releases/4.0/#zoneinfo-default-timezone-implementation
• Do we have to change logout? https://docs.djangoproject.com/en/5.0/releases/4.1/#log-out-via-get
• Do we have custom Model.save implementations? https://docs.djangoproject.com/en/5.0/releases/4.2/#setting-update-fields-in-model-save-may-now-be-required
• Consider switching from pwgen to Python's built-in secrets. Secrets seems to be considered good by Django, see https://docs.djangoproject.com/en/5.0/releases/4.2/#id1.