AddMessagesToMailbox adds the messages to the given mailbox.

MoveMessagesFromMailbox moves messages from one mailbox to the other.

NewStateContext will annotate a context object with the state's assigned ID.

RemoveMessagesFromMailbox removes the messages from the given mailbox.

ExistsStateUpdate needs to be a separate update since it has to deal with a Recent flag propagation.

State represents the active session's state after a user has been authenticated.

Connector interface for State differs slightly from the connector.Connector interface as it needs the ability to generate internal IDs for each request as well as track local metadata associated with each state.

UserInterface represents the expected behaviour for interacting with a remote user.