Update to version 3.8.0

src/AsyncJson.h

@@ -4,8 +4,14 @@
 #ifndef ASYNC_JSON_H_
 #define ASYNC_JSON_H_
 
+#if __has_include("ArduinoJson.h")
 #include <ArduinoJson.h>
+#if ARDUINOJSON_VERSION_MAJOR >= 5
 #define ASYNC_JSON_SUPPORT 1
+#else
+#define ASYNC_JSON_SUPPORT 0
+#endif  // ARDUINOJSON_VERSION_MAJOR >= 5
+#endif  // __has_include("ArduinoJson.h")
 
 #if ASYNC_JSON_SUPPORT == 1
 #include <ESPAsyncWebServer.h>
@@ -73,7 +79,6 @@ protected:
   String _uri;
   WebRequestMethodComposite _method;
   ArJsonRequestHandlerFunction _onRequest;
-  size_t _contentLength;
 #if ARDUINOJSON_VERSION_MAJOR == 6
   size_t maxJsonBufferSize;
 #endif