Should be able to create branch permissions with no users or groups

There are times where our software managers want to (temporarily) prevent changes from being committed and/or merged into a branch.

To do this, I would like to be able to remove all users or groups from the repo's branch permission settings. WIth no users or groups, no one should be able to make changes. Unfortunately, Stash does not allow this. An inelegant workaround is to replace valid users with a placeholder service account when we want to restrict access. But that's not really satisfying the requirement, as theoretically that service account could make changes to the branch.