MergeRequest#merge_jid should be cleaned up whenever we hit a known error on
MergeService#execute (or we finished processing). This way we can keep track if the MR is really "ongoing" or just "stuck" (stuck MRs are already being handled by
Currently, if a an user clicks
Merge and the MR is not mergeable, or no source is found, we keep stuck on
merge ongoing state.
Does this MR meet the acceptance criteria?
Changelog entry added, if necessary
API support added
Tests added for this feature/bug
Has been reviewed by Backend
Conform by the [merge request performance guides](https://docs.gitlab.com/ee/development/merge_request_performance_guidelines.html)
Conform by the style guides
Squashed related commits together
What are the relevant issue numbers?
Closes #38476 (closed)