Use new refunds endpoint, accept either charge id or payment intent id

src/Message/RefundRequest.php

@@ -6,6 +6,8 @@
 
 namespace Omnipay\Stripe\Message;
 
+use Omnipay\Stripe\Message\PaymentIntents\AbstractRequest;
+
 /**
  * Stripe Refund Request.
  *
@@ -108,9 +110,27 @@ public function setReverseTransfer($value)
         return $this->setParameter('reverseTransfer', $value);
     }
 
+    /**
+     * @return mixed
+     */
+    public function getPaymentIntentReference()
+    {
+        return $this->getParameter('paymentIntentReference');
+    }
+
+    /**
+     * @param string $value
+     *
+     * @return AbstractRequest provides a fluent interface.
+     */
+    public function setPaymentIntentReference($value)
+    {
+        return $this->setParameter('paymentIntentReference', $value);
+    }
+
     public function getData()
     {
-        $this->validate('transactionReference', 'amount');
+        $this->validate('amount');
 
         $data = array();
         $data['amount'] = $this->getAmountInteger();
@@ -123,11 +143,23 @@ public function getData()
             $data['reverse_transfer'] = 'true';
         }
 
+        if ($this->getPaymentIntentReference()) {
+            $data['payment_intent'] = $this->getPaymentIntentReference();
+        }
+
+        if ($this->getTransactionReference()) {
+            $data['charge'] = $this->getTransactionReference();
+        }
+
+        if (!$this->getTransactionReference() && !$this->getPaymentIntentReference()) {
+            throw new \Omnipay\Common\Exception\InvalidRequestException('Either transactionReference or paymentIntentReference is required.');
+        }
+
         return $data;
     }
 
     public function getEndpoint()
     {
-        return $this->endpoint.'/charges/'.$this->getTransactionReference().'/refund';
+        return $this->endpoint.'/refunds';
     }
 }

src/Message/Response.php

@@ -96,6 +96,9 @@ public function getTransactionReference()
         if (isset($this->data['error']) && isset($this->data['error']['charge'])) {
             return $this->data['error']['charge'];
         }
+        if (isset($this->data['object']) && 'refund' === $this->data['object']) {
+            return $this->data['charge'];
+        }
 
         return null;
     }