Group only assignation
Context: At my company, we use Redmine in a project with a client. The client's users all have the role of 'Reporter' and we have two groups (the client's and the developer's groups). As things stand, whenever someone reports a Bug, it's always intended to come to our side, but to no one in particular, but the groups are the last option in the 'Assignee' field, forcing a user to scroll in order to even notice that there are groups in the list.
Goal: I would like it if whenever an issue (preferably only in the tracker 'Bugs' but not necessary) is created a person is forced to assign the issue to a group. It's possible to ask people to please follow the convention but I would prefer it for the software to be able to enforce it.
I tried looking for settings that would allow for this behaviour but was unable to find it.
Any help would be much appreciated.