A send answered without an EmailSubmission threw a fixed English
message, which the composer showed as is in every language. It now
throws `SendUnconfirmedError`, and the composer shows the existing
`send_timeout` text, the same advice as for a send whose answer was
lost: check Sent before sending again.
When the response carries no EmailSubmission - a method error, or no
answer for it at all - nothing confirms the message left, yet the send
went on as if it had: the old draft was replaced and the composer
closed. It now fails with "Send confirmation was not received" and
keeps the draft, so the user can check Sent before sending again.
An empty notCreated map is a success some servers spell out; it is no
longer read as a failure.
Drafts were saved without In-Reply-To and References, and a draft
re-opens in compose mode, where the composer has no original message to
rebuild them from. A reply that was saved and re-opened, or sent and
brought back with Undo, therefore went out as a new conversation.
`createDraft` now stores the threading headers, the composer saves them
with every draft of a reply, and re-opening a draft carries them into
the composer for later saves and the send.
Linus Rath
lucamzanon