fixup! Improving ESP32 ota to be inline with new IoTCloud implementation

Author: andreagilardoni

src/Arduino_ESP32_OTA.h

@@ -97,9 +97,22 @@ class Arduino_ESP32_OTA
   // call progressDownload, until it returns OtaDownloadCompleted
   // returns the value in content-length http header
   int startDownload(const char * ota_url);
-  OTADownloadState progressDownload();
+
+  // This function is used to make the download progress.
+  // it returns 0, if the download is in progress
+  // it returns 1, if the download is completed
+  // it returns <0 if an error occurred, following Error enum values
+  int progressDownload();
+
+  // this function is used to get the progress of the download
+  // it returns a positive value when the download is progressing correctly
+  // it returns a negative value on error following Error enum values
   int downloadProgress();
 
+  // this function is used to get the size of the download
+  // 0 if no download is in progress
+  size_t downloadSize();
+
   virtual void write_byte_to_flash(uint8_t data);
   Arduino_ESP32_OTA::Error verify();
   Arduino_ESP32_OTA::Error update();
@@ -123,6 +136,9 @@ class Arduino_ESP32_OTA
     uint32_t          downloadedSize;
     uint32_t          writtenBytes;
 
+    // If an error occurred during download it is reported in this field
+    Error             error;
+
     // LZSS decoder
     LZSSDecoder       decoder;