newsupernova/vendor/magento/module-authorization/Model/Acl/Role/User.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Authorization\Model\Acl\Role;

/**
 * User acl role
 */
class User extends \Magento\Authorization\Model\Acl\Role\Generic
{
    /**
     * All the user roles are prepended by U
     *
     */
    const ROLE_TYPE = 'U';
}