This library is released to Hackage as snaplet-sqlite-simple-jwt-auth.
See the https://github.com/nurpax/snap-reactjs-todo project for a full application using this library. It implements a todo application as an SPA using React and Redux with a Haskell API server running on Snap and uses this library to implement logins and route authentication. This blog post has a walk-through of the application's source code.