Two bugs an e2e test found the moment one existed for this path.
A private message the server held while we were offline arrives with
new_message false, and the handler only acknowledged the ones flagged
new — so exactly the messages that need an ack never got one and the
server re-delivered them at every login, forever. Every delivery is now
acknowledged.
A dropped Client also left its server connection open, so the session
lived on: mail addressed to us went to a socket nobody was reading and a
later login collided with our own ghost. Client::disconnect closes the
server and peer connections, and Drop calls it.
Also covers two features that were never driven end to end: an offline
message delivered once and not again, and a wishlist search answered like
any other.
Michel de Graaf
f5a97744f8