set default saml attrMapUsername

packages/app/src/server/routes/login-passport.js

@@ -468,7 +468,7 @@ module.exports = function(crowi, app) {
     const providerId = 'saml';
     const strategyName = 'saml';
     const attrMapId = crowi.configManager.getConfig('crowi', 'security:passport-saml:attrMapId');
-    const attrMapUsername = crowi.configManager.getConfig('crowi', 'security:passport-saml:attrMapUsername');
+    const attrMapUsername = crowi.configManager.getConfig('crowi', 'security:passport-saml:attrMapUsername') || 'username';
     const attrMapMail = crowi.configManager.getConfig('crowi', 'security:passport-saml:attrMapMail');
     const attrMapFirstName = crowi.configManager.getConfig('crowi', 'security:passport-saml:attrMapFirstName') || 'firstName';
     const attrMapLastName = crowi.configManager.getConfig('crowi', 'security:passport-saml:attrMapLastName') || 'lastName';