Tokens im eigenen Backend ausstellen

// Your backend — the app never sees the server secret.
const res = await fetch("https://engine.udt-stream.com/api/v1/token", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "X-App-Secret": process.env.UTD_SERVER_SECRET,   // never ship this in the app
  },
  body: JSON.stringify({
    user_id: currentUser.id,
    room_id: roomId,

    // 🔴 The user's own IP, not your server's. Without it every user of yours
    // is placed and geo-located as if they sat in your data centre.
    client_ip: req.headers["x-forwarded-for"]?.split(",")[0]?.trim() ?? req.ip,

    // 🔴 Forwarded FROM THE APP. Your server cannot know these on its own,
    // and without device_id one-account-one-device stops working for your users.
    device_id: body.device_id,
    device_model: body.device_model,
    os: body.os,
    os_version: body.os_version,
    app_version: body.app_version,
  }),
});

// Your app — send the device facts to YOUR backend, which forwards them to us.
final deviceId = await MyDeviceIdentity.stableId(); // persisted, survives app restarts
await myApi.post("/rooms/$roomId/token", body: {
  "device_id": deviceId,
  "device_model": deviceInfo.model,
  "os": Platform.isAndroid ? "android" : "ios",
  "os_version": deviceInfo.version,
  "app_version": packageInfo.version,
});