feat(CI): add MR comments for previews, refactor anchors and extends
This adds comments to open MRs, when a new preview build has been pushed to an ad hoc GitLab MR CI Artifacts preview environment.
A little refactoring around the .build-default
anchor was needed to reduce code duplication.
It appeared useful for visualising the changes for long-running branches and MRs such as !84 (merged), where the preview environment frequently goes through different iterations.
Edited by jon r