RegistryConstants.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Magento\CatalogRule\Controller;

/**
 * Declarations of core registry keys used by the CatalogRule module
 *
 */
class RegistryConstants
{
    /**
     * Key for current catalog rule in registry
     */
    const CURRENT_CATALOG_RULE_ID = 'current_promo_catalog_rule';
}