Moving a forum with "Leave shadow copy" checked should leave a copy in the original forum

Forum is approved for removal. See #1898812: [policy] Deprecate forum module for removal in Drupal 11 →

This is now Postponed. The status is set according to two policies. The Remove a core extension and move it to a contributed project → and the Extensions approved for removal → policies.

It will be moved to the contributed extension → once the Drupal 11 branch is open.

eelkeblok → changed the visibility of the branch 2390065-rebase-10-2 to hidden.

I took the liberty of creating an MR against Drupal 11 so folks who need a patch can get one (copy the contents of https://git.drupalcode.org/project/drupal/-/merge_requests/6674.diff to your local project and apply the patch). There was a conflict with #57 and some recent changes to the module file.