Mobile-web parity MW-19 slice. Add subscribe and unsubscribe actions to merge request detail. Model unknown subscription state, handle GitLab's idempotent HTTP 304 response, map permission and transport errors, and cover API/controller/widget behavior with tests. Keep this separate from issue to-do PR #334.
Mobile-web parity MW-19 slice. Add subscribe and unsubscribe actions to merge request detail. Model unknown subscription state, handle GitLab's idempotent HTTP 304 response, map permission and transport errors, and cover API/controller/widget behavior with tests. Keep this separate from issue to-do PR #334.