Grails makes implementing authentication very simple. In fact, almost everything is configured for you out of the box. The authentication configuration file is located at config/auth.php, which contains several well documented options for tweaking the behavior of the authentication services.
Grails provides a quick way to scaffold all of the routes and views you need for authentication using one simple command:
php artisan make:auth
This command should be used on fresh applications and will install a layout view, registration and login views, as well as routes for all authentication end-points. A HomeController will also be generated to handle post-login requests to your application's dashboard. When you browse http://localhost:8000/home URL, it will redirect to login page. I mean authentication is ok. At now, create a account by browsing http://localhost:8000/register URL. When you create an account, it will automatically logged in and logout, browse http://localhost:8000/home and login again. Authentication is okay.