feat: move webfinger endpoint to an api route

public/.well-known/webfinger

···
-{
-  "subject": "acct:[e-mail]",
-  "links": [
-    {
-      "rel": "http://openid.net/specs/connect/1.0/issuer",
-      "href": "https://sso.hayden.moe/application/o/tailscale/"
-    }
-  ]
-}

src/pages/.well-known/webfinger.ts

···
+import type { APIContext } from "astro";
+
+export const prerender = false;
+
+export const GET = async (c: APIContext) => {
+  const res = c.url.searchParams.get('resource');
+  if (!res) {
+    return Response.json({ error: 'missing resource query' }, { status: 400 });
+  }
+
+  if (!res.startsWith('acct:')) {
+    return Response.json({ error: 'this endpoint only supports acct: resources' }, { status: 400 });
+  }
+
+  return Response.json({
+    subject: res,
+    links: [
+      {
+        rel: "http://openid.net/specs/connect/1.0/issuer",
+        href: "https://sso.hayden.moe/application/o/tailscale/"
+      }
+    ]
+  });
+}