2FA + JWT how to do?

Question

API

There is a simple authorization service that issues, checks JWT, saves users in the database. I want to add the 2fa feature, for example, the OTP code from the application or to the mail (let it be sent to the mail for example). Service as an API.
Everything happens in an elementary way - the user enters login data on the front, the front sends to the api, the api returns the answer. How to correctly add a two-factor to such a scheme? Some intermediate state is needed - i.e. The user logged in, but did not enter the code? How is it customary to store it? No session - JWT. In general, how is it usually implemented in such services?

Answer 1

All intermediate states are the client side + mathematical algorithm + timer / code.
You need to keep the procedure and update the verification code (if necessary) without re-authorization.