* updated ruby to 2.7.5
* updated rails to 7.0.3
* switched devise_token_auth to git for rails7 support
* ran `rails app:update`
* cleanup .gitlab-ci.yml
* remove unnecessary ci files
* remove unused docker rake task
* fix potential inconsistent image build by using commit images as base
It would have been nicer to also exclude the test and spec folder within
the production container, saving some space within that, but the docker
COPY statement doesn't allow for that without a workaround. So this is
what we will do for now I guess.
Thor77
Daniel Schädler