apex.class

global class SamlConnectedAppPlugin extends Auth.ConnectedAppPlugin{
    global override boolean authorize(Id userId, Id connectedAppId, boolean isAdminApproved) {
        User u = [select id, First_SAML_Login__c from User where id =: userId].get(0);
        if(u.First_SAML_Login__c == null){
            u.First_SAML_Login__c = System.now();
            try{
                update u;
            }catch(exception e){
                System.debug('Exception:' + e.getMessage());
            }
        }
        return true;
    }

    //Return a user’s permission set assignments
    global override Map<String,String> customAttributes(Id userId, Map<String,String> formulaDefinedAttributes) {  
        User u = [select id, Name, CommunityNickname from User where id =: userId];
        formulaDefinedAttributes.put('nickname',u.CommunityNickname);
        formulaDefinedAttributes.put('fullname',u.Name);
        return formulaDefinedAttributes;
    }
}