I found Friend to be very opinionated and designed for a specific use case. I ended up rolling my own solution using Buddy (an excellent set of tools!).
I don’t think this is a solved problem. The FAQ for Sente (which I use) says:
“How do I integrate Sente with my usual login/auth procedure?
This is trivially easy as of Sente v0.13.0+.”
I think this is far from trivial and this area is still looking for a good library. Buddy is great, but it’s a set of screwdrivers, essentially, not an authentication and user management solution for webapps.