Not all states handle all protocol messages

[schuster]

There are a few instances in which a server in a given state will not handle a given protocol message. Usually these messages would not be sent to servers in such states, but if a message is delayed long enough for the recipient to change states before receiving it, the message might arrive in that later state.

Instances found:

• Follower does not handle VoteCandidate, DeclineCandidate, AppendSuccessful, or AppendRejected
• Leader does not handle RequestVote
• Candidate does not handle AppendSuccessful or AppendRejected