Impl - Handle Peer Remove

Being a removed node, once we can see consensus on Observation::Remove(Us), every subsequent call (it can be seen as the last stable block in consensused_blocks is Observation::Remove(Us)) to vote_for(), handle_request(), handle_response(), create_gossip() and poll() must incur an error to be raised.

Once we reach consensus on Observation::Remove(X), remove the node from our peer_manager(), which means that any future create_gossip, handle_request or handle_response to or from that node would err as per normal rules.

• If some node contacts us and this leads to us learning that Observation::Remove(them) reaches consensus, we send them a response as normal. This will inform them they were removed.

  • If they had been malicious and had contacted us after their own death, we would not have gotten to that point, thanks to normal malice handling rules

When some other node reaches consensus on Observation::Remove(X), we must update the state of their membership in peer_manager so we can easily detect Malice::InvalidGossipCreator from them later.