fix issue where an auto-redirect to SSO on login route was failing if invoked via API call (ajaxify)

src/controllers/index.js

@@ -131,7 +131,7 @@ Controllers.login = function (req, res, next) {
 	if (!data.allowLocalLogin && !data.allowRegistration && data.alternate_logins && data.authentication.length === 1) {
 		if (res.locals.isAPI) {
 			return helpers.redirect(res, {
-				external: data.authentication[0].url,
+				external: nconf.get('relative_path') + data.authentication[0].url,
 			});
 		}
 		return res.redirect(nconf.get('relative_path') + data.authentication[0].url);