Magento 2 – Get Coupon Code for Order in Order Success Observer

I created an observer with event checkout_onepage_controller_success_action. I need applied coupon code on checkout onepage success in magento 2. I have to send order coupon code to third party with Curl. Do you know, how we can retrieve coupon code used for the order on order success page?

Here is my observer code:

$orderIds = $observer->getEvent()->getOrderIds();
$lastorderId = $orderIds[0];
$order = $this->orderFactory->load($lastorderId);
// echo $order->getQuoteId(); // show quote ID
// echo $order->getDiscountAmount(); // show discount amount

/* Here I need applied Coupon Code */