When an IMAP client stores the `Forward` or `$Forward` flags on a message, the forwarded state is now correctly represented on the Proton servers. https://github.com/ProtonMail/go-proton-api/pull/125 https://github.com/ProtonMail/gluon/pull/400
Handles all IMAP related tasks. Unlike the previous iteration, this new service automatically adds and removes users from Gluon by interfacing with server manager.
