Update auth.rst

Need to do table instead of repository in UsersTable model.

namespace App\Model\Table;

use Cake\ORM\Table;
use Cake\Validation\Validator;
class UsersTable extends Table {
    public function validationDefault(Validator $validator) {
      return (array)$validator->notEmpty('username', 'A username is required')
            ->notEmpty('password', 'A password is required')
            ->notEmpty('role', 'A password is required')
            ->add('role', [
                'rule' => ['inList', ['admin', 'author']],
                'message' => 'Please enter a valid role'
            ]);
    } 
}

instead of : -
// App/Model/Repository/UsersTable.php
namespace App\Model\Repository;

use Cake\ORM\Table;

class UsersTable extends Table {

    public function validationDefault(Validator $validator) {
        return $validator
            ->notEmpty('username', 'A username is required')
            ->notEmpty('password', 'A password is required')
            ->notEmpty('role', 'A password is required')
            ->add('role', [
                'rule' => ['inList', ['admin', 'author']],
                'message' => 'Please enter a valid role'
            ]);
    }

}

still validations are not working.