Merge pull request #4731 from erikxiv/fix/techdocs-static-url

Techdocs static docs should use external url

.changeset/itchy-items-serve.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs-backend': patch
+---
+
+Use external url for static docs

plugins/techdocs-backend/src/service/router.ts

@@ -108,7 +108,7 @@ export async function createRouter({
     const { kind, namespace, name } = req.params;
     const storageUrl =
       config.getOptionalString('techdocs.storageUrl') ??
-      `${await discovery.getBaseUrl('techdocs')}/static/docs`;
+      `${await discovery.getExternalBaseUrl('techdocs')}/static/docs`;
 
     const catalogUrl = await discovery.getBaseUrl('catalog');
     const triple = [kind, namespace, name].map(encodeURIComponent).join('/');