How to Integrate Notifications in EDD Gateways

/**
* Insert payment gateway metadata and trigger notifications.
*
* @since            1.0.1
* @param int        $order_id Order ID associated with the payment.
* @param string     $channel  Payment gateway channel identifier.
* @param string     $link     URL link to the payment gateway.
* @param string|int $expires  Expiration timestamp or date string.
* @return void
*/
function edd_gateways_insert( $order_id, $channel, $link, $expires ) {
	$order_id = intval( $order_id );
	$channel  = esc_html( $channel );
	$link     = esc_url( $link );
	$expires  = ! is_numeric( $expires ) ? strtotime( $expires ) : intval( $expires );
 
	edd_update_order_meta( $order_id, EDD_PELATFORM_GATEWAYS . '_channel', $channel );
	edd_add_order_meta( $order_id, EDD_PELATFORM_GATEWAYS . '_link', $link );
	edd_add_order_meta( $order_id, EDD_PELATFORM_GATEWAYS . '_expires', $expires );
	do_action( 'edd_gateway_send_notifications', $order_id );
}