Event request - NO_EDGE_ROUTERS

[dovholuknf]

When a client successfully authenticates fully to an openziti overlay, if that user has NO edge routers whatsoever, that's a big deal. Right now we only discover this when trying to dial a service and look in the logs.

It would be much better to have an event after authentication containing how many edge routers are available. that way the UI could know if it's totally out of luck (no routers) or if it's expected to have at least one.

Any change in routers should trigger this event