Use snake_case for Connection etc methods

src/connection_handler.hpp

@@ -30,10 +30,10 @@ public:
    *
    * Implementation should:
    * - Parse incoming data using arena allocator when needed
-   * - Use conn_ptr->appendMessage() to queue response data to be sent
+   * - Use conn_ptr->append_message() to queue response data to be sent
    * - Handle partial messages and streaming protocols appropriately
    * - Can take ownership by calling conn_ptr.release() to pass to other threads
-   * - If ownership is taken, handler must call Server::releaseBackToServer()
+   * - If ownership is taken, handler must call Server::release_back_to_server()
    * when done
    * @note `data` is *not* owned by the connection arena, and its lifetime ends
    * after the call to on_data_arrived.