Implement shutting down the write-side only

tests/test_server.cpp

@@ -39,7 +39,7 @@ TEST_CASE("Echo test") {
     // MessageSender)
     auto *conn_ptr = static_cast<Connection *>(conn.get());
     conn_ptr->append_bytes(std::exchange(handler.reply, {}),
-                           std::move(handler.arena), false);
+                           std::move(handler.arena), ConnectionShutdown::None);
   } else {
     REQUIRE(false);
   }