Wrap cbuf inside AsyncResponseStream with a std::unique_ptr

Fraction of commit 8bb1c704cd70dd58b318b296154a5404a1bd27d0 of dumbfixes
branch of 0xFEEDC0DE64 fork of ESPAsyncWebServer.

Split off for clarity.

src/WebResponseImpl.h

@@ -27,6 +27,8 @@
 #undef max
 #endif
 #include <vector>
+#include <memory>
+
 // It is possible to restore these defines, but one can use _min and _max instead. Or std::min, std::max.
 
 class AsyncBasicResponse: public AsyncWebServerResponse {
@@ -122,7 +124,7 @@ class cbuf;
 
 class AsyncResponseStream: public AsyncAbstractResponse, public Print {
   private:
-    cbuf *_content;
+    std::unique_ptr<cbuf> _content;
   public:
     AsyncResponseStream(const String& contentType, size_t bufferSize);
     ~AsyncResponseStream();

src/WebResponses.cpp

@@ -675,16 +675,15 @@ size_t AsyncProgmemResponse::_fillBuffer(uint8_t *data, size_t len){
  * Response Stream (You can print/write/printf to it, up to the contentLen bytes)
  * */
 
-AsyncResponseStream::AsyncResponseStream(const String& contentType, size_t bufferSize){
+AsyncResponseStream::AsyncResponseStream(const String& contentType, size_t bufferSize)
+{
   _code = 200;
   _contentLength = 0;
   _contentType = contentType;
-  _content = new cbuf(bufferSize);
+  _content = std::unique_ptr<cbuf>(new cbuf(bufferSize)); //std::make_unique<cbuf>(bufferSize);
 }
 
-AsyncResponseStream::~AsyncResponseStream(){
-  delete _content;
-}
+AsyncResponseStream::~AsyncResponseStream() = default;
 
 size_t AsyncResponseStream::_fillBuffer(uint8_t *buf, size_t maxLen){
   return _content->read((char*)buf, maxLen);