Merge pull request #17407 from backstage/jhaals/fixlink

microsite: migrate link page from old site

microsite/src/pages/link.tsx

@@ -0,0 +1,15 @@
+import { Redirect } from '@docusaurus/router';
+import React from 'react';
+
+const redirects = {
+  'bind-routes':
+    '/docs/plugins/composability#binding-external-routes-in-the-app',
+  'scm-auth': '/docs/auth/#scaffolder-configuration-software-templates',
+  'backend-system': '/docs/plugins/new-backend-system',
+};
+const fallback = '/docs';
+const target = redirects[global.window.location.search.slice(1)] || fallback;
+
+export default function Link() {
+  return <Redirect to={target} />;
+}