Allow adding an explanatory comment when editing several Issues at once

Steps to reproduce:

  1. Move a project with open Issues in GNOME's GitLab instance from one group to another group (called Archive, being a graveyard).
  2. Go to list of open issues in that very project, e.g. https://gitlab.gnome.org/Archive/someproject/-/issues
  3. Select Edit Issues in top bar
  4. Select all issues via checkboxes on the left
  5. Select some action(s) on the right, e.g. change Status dropdown on the right to Closed

Current behavior:

No way to explain the action that I am going to perform to the authors of and folks subscribed on those tickets

Screenshot_from_2020-11-13_23-39-30

Expected behavior:

  • A text field allowing to add a comment together with the other action(s) performed, e.g. to explain "This project has been moved to the Archived group hence closing all open Issues as no further work will take place."

Other comments:

  • I see that e.g. https://gitlab.com/gitlab-org/gitlab-foss/-/issues/new uses a template which says Please do not create issues here in the Description field, however that's only a path for new issues and not for existing ones.
  • I assume I could use the API as a fallback for this. That'll get more complex the more interesting the query and selection of Issues will be.

Feel free to decline this proposal if you think this "cleanup" use case is uncommon and admins should use the API instead.