Updated backend dependencies

[3top1a]

I have updated significant portions of the backend to use newer and better supported dependencies.

• Updated Dockerfile to use newest Ubuntu LTS image and Python 3.12.
• Cleaned up apt operations and made it use a virtual environment.
• Updated backend to use Django 4 and updated renamed methods.
• Updated most backend dependencies to newer supported versions.
• Replaced rest_auth with dj_rest_auth as it was not compatible.

This is required for further changes.

[3top1a]

The tests currently do not work, but they were not working prior to this as well.

[krab1k]

Hi @veitveit, @anitamnd. This is a batch of patches to use as a base for further changes. It also promotes packages to supported versions. Please review this PR and drop us a line with feedback. Thanks a lot!