pub fn sign_message(
identity: &Identity,
msg: &RoomMessage,
) -> Result<SignedRoomMessage>Expand description
Wrap a RoomMessage into a SignedRoomMessage using the given
identity’s signing key. Mirror of verify_signed; symmetric helper
so phase B/F/G/etc. don’t each open-code the base64 dance.
huddle 0.7.11: also populates signed_at_ms with the current epoch
in milliseconds, and signs over (payload || signed_at_ms) so the
receiver’s replay-window check is signature-bound.