[keycloak-user] Using another name than Keycloak's?

Hi, We're attempting to protect a service using Keycloak. We've noticed that some values that are valid usernames in Keycloak, are not valid in our service. We'd like to be able to use a username in our service that's different from the username that is used in Keycloak. Preferably, we'd like Keycloak to store the association between 'our' username and the Keycloak user. Is something like this feasible with the existing integration features that are offered by Keycloak? Regards, Guus