Fix integration "#hook" link using wrong base domain

Author: pjcdawkins

src/Model/Integration.php

@@ -39,6 +39,27 @@ public function triggerHook()
         $this->sendRequest($hookUrl, 'post', $options);
     }
 
+    /**
+     * {@inheritDoc}
+     *
+     * The hook link must use the integration's "self" link as the base, not
+     * the overridden base URL. This is because the external API proxy does not
+     * yet support unauthenticated requests.
+     */
+    public function getLink($rel, $absolute = true)
+    {
+        if ($rel === '#hook') {
+            if (!isset($this->data['_links'][$rel]['href'])) {
+                throw new \InvalidArgumentException("Link not found: $rel");
+            }
+            if (!isset($this->data['_links']['self']['href'])) {
+                throw new \RuntimeException('Failed to find integration "self" link');
+            }
+            return $this->makeAbsoluteUrl($this->data['_links'][$rel]['href'], $this->data['_links']['self']['href']);
+        }
+        return parent::getLink($rel, $absolute);
+    }
+
     /**
      * Validate the integration via the API.
      *