How did you link an unauthenticated user's subscription with their account after authentication?

To link an unauthenticated user's subscription with their account after login, a temporary identifier is usually used, such as a cookie or localStorage, which stores subscription information until login. After login, this identifier is linked to the user's account in the database, and the subscription is transferred to their profile.

Example:

1. The user subscribes without logging in, and the system saves the subscriptionId in a cookie.
2. After login, the backend retrieves the subscriptionId from the cookie and links the subscription to the userId.
3. The cookie is cleared to prevent duplication.

This ensures a seamless transition and preservation of user data.