OpenAPI: Export images written and images with write error

image_pusher/TCPStreamPusher.cpp

@@ -1131,3 +1131,7 @@ std::string TCPStreamPusher::PrintSetup() const {
 std::optional<uint64_t> TCPStreamPusher::GetImagesWritten() const {
     return total_data_acked_ok.load(std::memory_order_relaxed);
 }
+
+std::optional<uint64_t> TCPStreamPusher::GetImagesWriteError() const {
+    return total_data_acked_bad.load(std::memory_order_relaxed);
+}