exclude registration from laravel auth
Laravel 5.7 introduced the following functionality:
	Auth::routes(['register' => false]);
The currently possible options here are:
  Auth::routes([
    'register' => false, // Registration Routes...
    'reset' => false, // Password Reset Routes...
    'verify' => false, // Email Verification Routes...
  ]);
For older Laravel versions just override showRegistrationForm() and 
register() methods in
AuthController for Laravel 5.0 - 5.4
Auth/RegisterController.php for Laravel 5.5
public function showRegistrationForm()
{
    return redirect('login');
}
public function register()
{
}
