I am currently building ( https://tryonzauth.com ), basically to solve this problem, which I myself find painful, first thing I always build is authentication/login. With this solution, you can add authentication within 5mins with the SDK, ease the signup process (no forget password etc...), using magic link passwordless authentication. JWT token is just a standard token where most languages got libraries to read it (email claims) etc...

Focus on building your product, and it's free to get started. Free tier atm is about 2.5k active users per month, but not set in stone yet.

We are looking for feedbacks and features suggestions, to get to our MVP/Beta version, currently in alpha/testing phase.