OAM 12c SAML Response needs value in firstname.lastname format in the response

Requirenment. We need to achieve a reuirenment where SAML response should be firstname.lastname but our username attribute from the OUD have email address. Tableau require username attribute in this formate. Solution. In a SAML response we have to contatinate the firstname and lastname values to achieve username attribute value here is the expresion we used in the SAML response username value. ${user.attr.givenname}.${user.attr.sn} results was firstname.lastname