Dockerfile better entrypoint

[simonseyock]

This is a draft for solving #937

It is not fully tested.

[simonseyock]

This is now fully tested. The CI process is not yet adapted.

[simonseyock]

I updated the dockerbuild github action. I removed the workflow_dispatch trigger because:
a) it made the action way more complicated (double build definitions for every flavor)
b) a dockerfile should always correspond to a git tag imho. so if a tag should be republished it needs to be deleted and recreated

Here is an example workflow run without pushing the images: https://github.com/simonseyock/mapproxy/actions/runs/9774970243/job/26984393702

[weskamm]

I updated the dockerbuild github action. I removed the workflow_dispatch trigger because: ...

As long as we dont need to publish older images again (which i currently see no reason for), this should be fine

[weskamm]

Thanks for your work! Lets see if tests from Hannes succeed before merging, but you get my thumbs up!

[hblitza]

Thanks @simonseyock. I tested it locally - successfully for dev,plain,nginx both alpine and debian.