api/url: add function for resolving shortlinks

motivation: we frequently need to resolve shortlinks to full URLs
let's have a common standard function for doing this safely
instead of reinventing the wheel in every single service module

api/src/misc/utils.js

@@ -1,12 +1,13 @@
+import { request } from 'undici';
 const redirectStatuses = new Set([301, 302, 303, 307, 308]);
 
-export async function getRedirectingURL(url, dispatcher) {
-    const location = await fetch(url, {
-        redirect: 'manual',
-        dispatcher,
-    }).then((r) => {
-        if (redirectStatuses.has(r.status) && r.headers.has('location')) {
-            return r.headers.get('location');
+export async function getRedirectingURL(url, dispatcher, userAgent) {
+    const location = await request(url, {
+        dispatcher, method: 'HEAD',
+        headers: { 'user-agent': userAgent }
+    }).then(r => {
+        if (redirectStatuses.has(r.statusCode) && r.headers['location']) {
+            return r.headers['location'];
         }
     }).catch(() => null);