Middleware support?

I was trying to find find documentation of how to add custom middlewares? An example would be an auth middleware that checks whether user is logged in or not. How would you achieve that with bud?

The issue names no file, test, or entry point. Review Bud's existing middleware documentation and request-handling entry points, then document how to register custom middleware with an authentication example and explain how to verify that unauthenticated requests are handled.

Written by the indexing model from the issue text.