[keycloak-user] Mapper for External Identity provider

Hi, While configuring Keycloak as SP with ADFS 2.0 as external IDP, the user authentication fails in my app's backend after passing the credentials in ADFS login page. On investigating, Found out that the Username of the external user is stored by his email address in Keycloak-Users while the username is configured as "LDAP entry dn" for internal users in keycloak. I wish to get the DN of this external user in the username field. Do we need to configure a mapper for the same?