Tagged releases do not create images
Currently because our tagged releases start with word release
they are not caught by the TAG_REGEX in ci_image_build.sh
https://gitlab.eox.at/esa/prism/vs/-/blob/staging/ci_image_build.sh#L11-15
Solution: there is a CI env variable CI_COMMIT_TAG
which can be used to know if we are doing this for a tag or not.
https://docs.gitlab.com/ee/ci/variables/#list-all-environment-variables