Check Django 5 compatibility

[knabar]

Django 5.0.3 is now available, we should check if any changes are required to support it.

Note: Django 5 only supports Python 3.10+, so Django 4 support will be required for now as well.

[jburel]

@knabar is it something to consider in the CI as part of the adjustments for Java version upgrade.
Alternatively, I could prepare a second CI with Python 3.10 so we do not affect merge-ci for now