Send a message again as a new one

A mail the far end rejected, or one that went to an address with a typo in
it, is a mail you want to send again -- not forward, and not reply to.
Doing it by hand meant a new message and copying five fields across.

"Compose as new" sits with Reply and Forward, in the message menu and in
the list's right-click menu. It opens a composer holding the recipients
the message had, its Reply-To, its subject with nothing prefixed to it,
its body with nothing wrapped around it, and its attachments.

What makes it a new mail is what it leaves behind. `draftId` stays null,
or sending would destroy the message it was made from. `inReplyTo`,
`references`, `relatedEmailId` and `relatedKeyword` stay null, so it hangs
off no thread and sending it marks the original neither answered nor
forwarded. The Message-ID is the server's and the date is stamped at
build time, so both are new without anything asking for them -- the send
path needed no changes at all.

A message you sent is composed as the identity you sent it as. One
somebody else sent has no identity of yours to match, and guessing from
whom it was addressed to would put the resend behind an alias that was
only ever the receiving end, so that case takes the account's default.

No signature is added. The body is the one that was sent, which already
ends in whatever signature went with it, and appending the identity's
would give it two.

Closes #176

web/src/views/mail/MessageView.tsx

@@ -1,5 +1,5 @@
 import { memo, useCallback, useEffect, useMemo, useRef, useState } from "react";
-import { ChevronDown, ChevronUp, Download, ExternalLink, Forward, MoreVertical, Printer, Reply, ReplyAll, Star, Trash2, Code, FileText, Image as ImageIcon, File, Eye, Calendar, CalendarPlus, UserPlus, ShieldAlert, Mail, Ban, Clock, CheckCheck, Paperclip, FileArchive, FileSpreadsheet, Film, Music, Filter } from "lucide-react";
+import { ChevronDown, ChevronUp, Download, ExternalLink, Forward, MailPlus, MoreVertical, Printer, Reply, ReplyAll, Star, Trash2, Code, FileText, Image as ImageIcon, File, Eye, Calendar, CalendarPlus, UserPlus, ShieldAlert, Mail, Ban, Clock, CheckCheck, Paperclip, FileArchive, FileSpreadsheet, Film, Music, Filter } from "lucide-react";
 import { useLocation } from "wouter";
 import { FilterFromMessageDialog } from "./FilterFromMessage";
 import type { Email, EmailAddress, EmailBodyPart, Id } from "@/jmap/types";
@@ -190,6 +190,9 @@ export const MessageView = memo(function MessageView({ email: e, expanded, wasUn
         <MenuItem icon={<Reply size={16} />} label={translate("Reply")} onClick={() => void reply(e, "reply")} />
         <MenuItem icon={<ReplyAll size={16} />} label={translate("Reply all")} onClick={() => void reply(e, "replyAll")} />
         <MenuItem icon={<Forward size={16} />} label={translate("Forward")} onClick={() => void reply(e, "forward")} />
+        {/* Sends the same mail again rather than passing it on, so it sits with
+            the other three rather than down among the read-only actions. */}
+        <MenuItem icon={<MailPlus size={16} />} label={translate("Compose as new")} onClick={() => void useCompose.getState().composeAsNew(e)} />
         <MenuSep />
         <MenuItem icon={<Mail size={16} />} label={e.keywords.$seen ? "Mark as unread" : "Mark as read"} onClick={() => void useMail.getState().markRead([e.id], !e.keywords.$seen)} />
         <MenuItem icon={<Trash2 size={16} />} label={translate("Delete this message")} onClick={() => void useMail.getState().trash([e.id])} />