[REQ] [cpprestsdk] ApiException is not used in the way it is generated

Is your feature request related to a problem? Please describe.

The generator produces code that uses ApiException not in the way it has been intended. Ok, this is not exactly true but let me show what I mean thanks to the PetApi example :

In the file PetApi.cpp line 136 we can see one error treatment throwing an ApiException

if (localVarResponse.status_code() >= 400)
        {
            throw ApiException(localVarResponse.status_code()
                , utility::conversions::to_string_t("error calling addPet: ") + localVarResponse.reason_phrase()
                , std::make_shared<std::stringstream>(localVarResponse.extract_utf8string(true).get()));
        }

The 3rd parameter of the ApiException is set with a std::make_shared<std::stringstream> whereas the ApiException shows the corresponding API with a std::shared_ptr<std::istream>

class  ApiException
    : public web::http::http_exception
{
public:
    ApiException( int errorCode
        , const utility::string_t& message
        , std::shared_ptr<std::istream> content = nullptr );
../..
}

Of course this is allowed because a std::stringstream IS A std::istream but when I (the developer) want to handle an ApiException in my application, I retrieve "'only" an std::istream that is not really convenient to use whereas at the origin, the ApiException has been raised with a std::stringstream.

Describe the solution you'd like

What about modifying the ApiException and replace the use of std::istream with std::stringstream ?

Describe alternatives you've considered

N/A

Additional context

N/A

Start with samples/client/petstore/cpp-restsdk/client/ApiException.h and the generated use in samples/client/petstore/cpp-restsdk/client/api/PetApi.cpp around line 136. Trace these files back to the generator source that produces them, then inspect related C++ REST SDK tests. Done means the generated exception interface supports the content type requested in the issue and the generated client remains consistent.