You are not over thinking things, it should not be relative. I kinda punted on this because I don't know how we're going to determine the fully qualified URL. In the past we've used an environment variable for this, and that's probably the best way to do it, though I suppose we could also generate it by introspecting the `Host` header on on the request (assuming we can also introspect from `req` whether the request was made over HTTP or HTTPS)