Refactor: define identifier format in single location
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=591376) </details> <!--IssueSummary end--> The following discussion from !221351 should be addressed: - [ ] @SamWord started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/221351#note_3107096860): (+3 comments) > **Thought (non-blocking):** It'd be nice if there could be one place where this identifier format is defined so that this module and [the metadata service](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/224143/diffs#19710768c38c1000d5e81e3a8ebf9d7d16860890_0_57) can share it. Non-blocking because I'm not really sure how to do that at the moment and the implementations of each are quite different
issue