Optionally skip copying into connection arena for appendMessage

src/connection.hpp

@@ -40,7 +40,7 @@ struct Connection {
   ~Connection();
 
   // Handler interface - public methods that handlers can use
-  void appendMessage(std::string_view s);
+  void appendMessage(std::string_view s, bool copyToArena = true);
   void closeAfterSend() { closeConnection_ = true; }
   ArenaAllocator &getArena() { return arena_; }
   int64_t getId() const { return id_; }