title: Manually set IIdentity
body: <p>I'm using my own authentication scheme, non-cookie based. I want to be able to manually set the <code>Controller.User.Identity</code> with username and other data that I would normally set in a FormsAuthentication Cookie. Currently, the User Identity is being set by FormsAuthentication (I have no idea how, it just reads it from the encrypted cookie). How does FormsAuthentication do it? How would I do it?</p>