[keycloak-user] Service account user attributes

Hello I would like to use service accounts to allow my OIDC clients to obtain access tokens using the client credentials grant. Furthermore, I'm trying to find a way to define additional attributes for each service account client so that I can map them to custom claims via a protocol mapper. I notice that Keycloak creates an internal user for each service account in its database, but the user is not visible/editable through the admin UI. Therefore, I am unable to create attributes for the service account user as I can for 'normal' users. I think I can define custom claims for a service account using a protocol mapper (something like the "hardcoded claim" mapper), assuming I can distinguish service account requests from user requests in the mapper. If this approach is not recommended, I would be very grateful if you could suggest an alternative. Kind regards Dan