Storage server, in particular, needs to disable pubkey-based routing on
its connection to oxend (because it is sharing oxend's own keys), but
wants it by default for SS-to-SS connections. This allows the oxend
connection to turn it off so that we don't have oxend omq connections
replacing each other.
This provides an interface for sending a reply to a message later (i.e.
after the Message& itself is no longer valid) by using a new
`send_later()` method of the Message instance that returns an object
that can properly route replies (and can outlive the Message it was
called on).
Intended use is:
run_this_lambda_later([send=msg.send_later()] {
send.reply("content");
});
which is equivalent to:
run_this_lambda_later([&msg] {
msg.send_reply("content");
});
except that it works properly even if the lambda is invoked beyond the
lifetime of `msg`.
