Add coupons to available variables

ordernumbers_woocommerce.php

@@ -324,6 +324,7 @@ class OpenToolsOrdernumbers extends OpenToolsOrdernumbersBasic {
 		$reps["[tags]"] = array_keys($tags);
 		$reps["[shippingclasses]"] = array_keys($shippingclasses);
 		$reps["[vendors]"] = array_unique($vendors);
+		$reps["[coupons]"] = $order->get_used_coupons();
 	}
 
 	public function setupUserReplacements (&$reps, $details, $nrtype) {