[keycloak-user] Change username?

Hi, is there any possibility to change the users username? The UI doesn’t provide a possibility (field is readonly) and via REST-Admin-API a changed username is ignored when updating the user. I understand that this is not easy to handle and maybe the username is a primary/unique key in the datastore. (But) we have the requirement that it must be able to change the users username. So, is there any possibility/workaround for this? Regards, - Niko