Greatly reduce repeated code

functions/api/gme/_middleware.ts

@@ -1,3 +1,5 @@
+import { jsonError } from "../../common.js";
+
 export async function onRequest(context: RequestContext) {
   const { current_user: currentUser } = context.data;
 
@@ -9,12 +11,7 @@ export async function onRequest(context: RequestContext) {
       "396347223736057866",
     ].includes(currentUser.id)
   )
-    return new Response('{"error":"Forbidden"}', {
-      headers: {
-        "content-type": "application/json",
-      },
-      status: 403,
-    });
+    return jsonError("Forbidden", 403);
 
   return await context.next();
 }