Dropping support for Python 3.8 at the end of the year

[vlaci]

Python 3.8 reached EOL on 2024-10-07. Our dependencies will likely drop support for that version as well, so it will be a burden to keep-up support for it sooner or later.

The plan is to release a final version supporting Python 3.8 at around December-January.

Should you have any questions or comments about the timeline, please comment on this issue.

[qkaiser]

A good first step would be to move away from python:3.8-slim in our Dockerfile ...