In stfc mode if a user has the user role and 1 other role that role cannot be removed

[TCMeldrum]

This is due to how we are handeling role assigments in the stfc user datasource. When we remove a role from them the frontend sends a request saying this users new roles should be [user]. The stfcuserdatasource then notices that the user role comes from uows removes that from the array, thinks there are no new roles to give that user so does not pass the empty array onto the postgress datasource.
https://github.com/user-attachments/assets/e6074999-ceec-4117-921f-54794f2f3ee9