Guards that trigger again on stream event

[lukepighetti]

Issue inspired by #213 (reply in thread)

Right now FluroGuard triggers when the route is pushed. But in the case of an authentication guard, who may have logged in status stream events, it would be ideal to have this guard run again when the auth state changes, not just on push checks.

Perhaps we could have FluroGuard and FluroGuard.stream?

My concern is that this will create UX anti-patterns. If an auth token expires, it should be refreshed. If a user explicitly logs out, a navigation route change should be dispatched at that time. Neither of those imply a stream triggered guard. But at the same time, there are likely use cases that I can't identify at this time. Perhaps the question is how to organize route permissions, route alternatives, and when those are resolved.