Register with ThinkTecture IdentityServer / STS / auth-based application

Question

I recently played with ThinkTecture IdentityServer, and I hooked up a simple project that used IdentityServer as an STS for claims-based federated authentication . Thus, the "login" works. Now I am trying to figure out how to allow registration.

With the entire IdentityServer / STS / Claims model, how can I allow users to register? I looked around and found almost nothing on this topic. This makes me wonder: do I need to do subscriptions using a separate service that writes to the same user store, common to IdentityServer / STS? Or is there another solution?

Disclaimer: I'm pretty new to the whole .NET Authentication / Authorization topic.