Greatly reduce repeated code

functions/api/gme/add.ts

@@ -1,21 +1,13 @@
-function makeResponse(body: string, status: number): Response {
-  return new Response(body, {
-    headers: {
-      "content-type": "application/json",
-    },
-    status,
-  });
-}
+import { jsonError } from "../../common.js";
 
 export async function onRequestPost(context: RequestContext) {
   const { user } = context.data.body;
 
-  if (!user) return makeResponse('{"error":"No user provided"}', 400);
+  if (!user) return jsonError("No user provided", 400);
 
   const existingUser = await context.env.DATA.get(`gamemod_${user}`);
 
-  if (existingUser)
-    return makeResponse('{"error":"Cannot add an existing user"}', 400);
+  if (existingUser) return jsonError("Cannot add an existing user", 400);
 
   if (
     ["165594923586945025", "289372404541554689", "396347223736057866"].includes(
@@ -26,8 +18,7 @@ export async function onRequestPost(context: RequestContext) {
       status: 204,
     });
 
-  if (!user.match(/^\d{17,19}$/))
-    return makeResponse('{"error":"Invalid User ID"}', 400);
+  if (!user.match(/^\d{17,19}$/)) return jsonError("Invalid User ID", 400);
 
   const data = { time: Date.now(), user: context.data.current_user.id };