Refactor code structure for improved readability and maintainability

server/middleware/auth.js

@@ -21,3 +21,13 @@ export async function requireAuth(req, res, next) {
         return res.status(401).json({ error: "Ongeldige of verlopen token." });
     }
 }
+
+export function requireAdmin(req, res, next) {
+    if (!req.user) {
+        return res.status(401).json({ error: "Inloggen vereist." });
+    }
+    if (!req.user.isAdmin) {
+        return res.status(403).json({ error: "Administratorrechten vereist." });
+    }
+    next();
+}