So first impression: isn't the FoAz proxy simply the backend? I apologize it that seems like a dumb question, I never used oauth or jwt.
To clarify - FoAz is frontend only - like Serverless has no servers :D
The idea is that as a FE developer you can consume this as a generic service once and for all, without constantly going back to backend and devops to set up glue code routes.
Feel free to follow up with more questions, especially if I wasn't clear enough