[keycloak-user] Idp attribute mapper lowercase

Is there any way with the default SAML Identity Provider Mappers in Keycloak to map the lowercase value of an attribute coming from the SAML response? I am attempting to add an Idp mapper to map the NAMEID attribute of the SAML response to the username (Which I believe is the default anyway) but the issue is that the attribute value is in all CAPS and I would like to keep the username in keycloak to all lowercase If not, can one easilly add new mappers? Regards Byte