CI: Extend CI_ENVIRONMENT_SLUG to 63 bytes
CI_COMMIT_REF_SLUG is shortened to 63 bytes. That's okay.
CI_ENVIRONMENT_SLUG seems to be shortened to only 24 bytes. That's a little too excessive. First, environment names are usually prefixed, e.g. review/. That alone leaves us with 17 "usable" bytes in the slug. Second, add a prefix developers use when naming a branch following the git-flow rules, e.g. feature/longer-ci-environment-slug-var, and feature/ gets us down to 9 usable characters. Then, 7 characters are used by GitLab slug generator. That means 2 usable characters for us. That's how our URLs look: https://review-feature-XY-ABCDEF.redacted.dreamhost.io/, and "feature-XY" comes from branch name.
If the reason for 24 byte limit was Kubernetes service name byte limit, it's been since fixed and extended to 63 bytes. https://github.com/kubernetes/kubernetes/pull/29523 https://github.com/fabric8io/fabric8-maven-plugin/pull/857