Image to debian bullseye

and split building and pushing image in CI.

I want to check whether we are able to build non-master branches, but I want to push to docker registry only from master branch.

changed the description

requested review from @mmatejek

assigned to @mmatejek

approved this merge request

Looks good, feel free to merge it.

assigned to @shenek and unassigned @mmatejek

merged