How to select users without any additional roles

Problem/Motivation

Any registered user has the "Authenticated user" role, so it doesn't really make sense to check for that.

For that reason, it might make sense to instead, to add an "(exclusively, no other roles)" or sth. like that behind that role and in the checks, check for the exclusive role. ("Only has" - just for that special case).

Steps to reproduce

Proposed resolution

Remaining tasks

Discuss
Implement
Write tests
Release

User interface changes

API changes

Data model changes