message: Add missing doc comments for `HandshakeOutcome`
diff: @@ -63,10 +63,15 @@ use crate::{
  /// successfully handed over to the kernel for sending.
  pub(super) type MessageQueueItem<P> = (Arc<Message<P>>, Option<AutoClosingResponder<()>>);
  +/// The outcome of the handshake process.
  struct HandshakeOutcome {
  + /// A framed transport for peer.
  framed_transport: FramedTransport,
  + /// Public address advertised by the peer.
  public_addr: SocketAddr,
  + /// The public key the peer is validating with, if any.
  peer_consensus_public_key: Option<PublicKey>,
  + /// True, if the peer identifies itself as "joiner".
  is_peer_joiner: bool,
  }
  