woocommerce/plugins/woocommerce-admin/includes/api/class-wc-admin-rest-reports-customers-controller.php

<?php
/**
 * REST API Reports customers controller
 *
 * Handles requests to the /reports/customers endpoint.
 *
 * @package WooCommerce Admin/API
 */

defined( 'ABSPATH' ) || exit;

/**
 * REST API Reports customers controller class.
 *
 * @package WooCommerce/API
 * @extends WC_REST_Reports_Controller
 */
class WC_Admin_REST_Reports_Customers_Controller extends WC_REST_Reports_Controller {

	/**
	 * Endpoint namespace.
	 *
	 * @var string
	 */
	protected $namespace = 'wc/v3';

	/**
	 * Route base.
	 *
	 * @var string
	 */
	protected $rest_base = 'reports/customers';
}