message: Improve logging in stream_serv implementation
diff: @@ -290,6 +290,7 @@ void middleman::start() {
  behavior make_behavior() override {
  return {
  [=](stream_msg& x) -> delegated<message> {
  + CAF_LOG_TRACE(CAF_ARG(x));
  // Dispatching depends on the direction of the message.
  if (outgoing_.has_stream(x.sid)) {
  outgoing_(x);
  @@ -299,13 +300,13 @@ void middleman::start() {
  return {};
  },
  [=](sys_atom, stream_msg& x) -> delegated<message> {
  - // Stream message received from a proxy, always results in a new
  - // stream from a local actor to a remote node.
  - CAF_ASSERT(holds_alternative<stream_msg::open>(x.content));
  + CAF_LOG_TRACE(CAF_ARG(x));
  + // Stream message received from a proxy
  outgoing_(x);
  return {};
  },
  [=](sys_atom, ok_atom, int32_t credit) {
  + CAF_LOG_TRACE(CAF_ARG(credit));
  CAF_ASSERT(current_mailbox_element() != nullptr);
  auto cme = current_mailbox_element();
  if (cme->sender != nullptr) {
  @@ -316,16 +317,19 @@ void middleman::start() {
  }
  },
  [=](exit_msg& x) {
  + CAF_LOG_TRACE(CAF_ARG(x));
  if (x.reason)
  quit(x.reason);
  },
  // Connects both incoming_ and outgoing_ to nid.
  [=](connect_atom, const node_id& nid) {
  + CAF_LOG_TRACE(CAF_ARG(nid));
  send(basp_, forward_atom::value, nid, atom("ConfigServ"),
  make_message(get_atom::value, atom("StreamServ")));
  },
  // Assumes `ptr` is a remote spawn server.
  [=](strong_actor_ptr& ptr) {
  + CAF_LOG_TRACE(CAF_ARG(ptr));
  if (ptr) {
  add_remote_path(ptr->node(), ptr);
  }
  @@ -334,6 +338,7 @@ void middleman::start() {
  }
  strong_actor_ptr remote_stream_serv(const node_id& nid) override {
  + CAF_LOG_TRACE(CAF_ARG(nid));
  strong_actor_ptr result;
  // Ask remote config server for a handle to the remote spawn server.
  scoped_actor self{system()};
  