Include credentials in fetch requests

Fixes #3701

Relevant spec section:
https://fetch.spec.whatwg.org/#concept-request-credentials-mode

ui/app/services/token.js

@@ -19,7 +19,7 @@ export default Service.extend({
     },
   }),
 
-  authorizedRequest(url, options = {}) {
+  authorizedRequest(url, options = { credentials: 'include' }) {
     const headers = {};
     const token = this.get('secret');