Implement MoveMessages in the imap backend. go-imap includes the MOVE
Imap extension by default, and if a server does not support it the
command fallsback to a copy-and-delete operation. Servers with the MOVE
extension will see a slight performance increase when moving messages
due to fewer round trips. The IMAP implementation uses a MessagesMoved
worker message to avoid polling the destination mailbox.
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>