Test deployment via SSH

Currently the jobs deploy_to_* in the gitlab-ci-project-template.yml (testing) checks only for expected tool to be available in the container.

Use a service or such to test the actual deployment to a server via rsync.

See https://dev.to/yakovlev_alexey/running-ssh-in-an-alpine-docker-container-3lop

For local testing:

docker run -it -p 2222:22  php:8.2-cli-alpine ash # install requirements
ssh root@127.0.0.1 -p 2222 # connect via ssh
rsync -rvz -e 'ssh -p 2222' ./ root@127.0.0.1:/docs/