We would like to trigger a CI job when a particular Milestone is set on an MR. Is this functionality supported by gitlab rules? We can certainly filter a job to run only if a particular Milestone is set, but that's not the use case here. Since this corresponds to neither branch nor merge pipelines, doing this through the API might be the only semi-automated option. But hopefully I missed something.
Gitlab seems to trigger pipelines only on commit or merge actions, but here the action is changing the Milestone on an existing MR without actually making a new commit, so it's unclear how to proceed other than manually re-running the pipeline.