add CancelSubscription at_period_end parameter

src/Message/CancelSubscriptionRequest.php

@@ -26,18 +26,44 @@ public function getSubscriptionReference()
     /**
      * Set the set subscription reference.
      *
+     * @param string $value
+     *
      * @return CancelSubscriptionRequest provides a fluent interface.
      */
     public function setSubscriptionReference($value)
     {
         return $this->setParameter('subscriptionReference', $value);
     }
 
+    /**
+     * Set whether or not to cancel the subscription at period end.
+     *
+     * @param bool $value
+     *
+     * @return CancelSubscriptionRequest provides a fluent interface.
+     */
+    public function setAtPeriodEnd($value)
+    {
+        return $this->setParameter('atPeriodEnd', $value);
+    }
+
+    /**
+     * Get whether or not to cancel the subscription at period end.
+     *
+     * @return bool
+     */
+    public function getAtPeriodEnd()
+    {
+        return $this->getParameter('atPeriodEnd');
+    }
+
     public function getData()
     {
         $this->validate('customerReference', 'subscriptionReference');
 
-        $data = array();
+        $data = array(
+            'at_period_end' => $this->getAtPeriodEnd()
+        );
 
         return $data;
     }