add lastEspErr variable to store esp32 camera api return values

In order to get more details on API failure reason, the return error
code needs to be stored and evaluated.

Author: alorbach

src/esp32cam.cpp

@@ -13,13 +13,15 @@ CameraClass Camera;
 bool
 CameraClass::begin(const Config& config)
 {
-  return esp_camera_init(reinterpret_cast<const camera_config_t*>(config.m_cfg)) == ESP_OK;
+  lastEspErr = esp_camera_init(reinterpret_cast<const camera_config_t*>(config.m_cfg));
+  return (lastEspErr == ESP_OK ? true : false);
 }
 
 bool
 CameraClass::end()
 {
-  return esp_camera_deinit() == ESP_OK;
+  lastEspErr = esp_camera_deinit();
+  return (lastEspErr == ESP_OK ? true : false);
 }
 
 bool

src/esp32cam.h

@@ -225,6 +225,10 @@ class CameraClass
     return streamMjpeg(client, StreamMjpegConfig());
   }
 
+  /** \brief Return value for esp API calls
+   *  \Store last api return value here useful for error handling!
+   */
+  esp_err_t lastEspErr; 
 
 };