Allow listing GROUPS in Board's assigned mode

We’re using Discourse Assign plugin to assign topics to a group, instead of individuals.

(In case you’re curious why: we handle requests on our community in teams, so we want to make sure every member of the team is promptly notified of new activities in their assigned topic.)

So we need a quick way to see the assigned topics and their status. The most suitable solution now is search using advanced filters. Example criteria: topics in AAA category, unsolved/solved status, assigned to BBB group. But it’s too manual and not visible and convenient enough.

Then we found the Board view which makes topic more visible and convenient. This means we can filter for the topic in AAA category, unsolved/solved status, buttttttttt we CANNOT filter for BBB group.

Would be great if group can be added to the Lists option too!