websocket_client and json::value are oil and water on Windows

[DHowett-MSFT]

• websocket_client allows you to receive message bodies as streams of uint8_t or as std::strings, which are both utf-8 (also, per specification, the only valid encoding for JSON is utf-8)
• json::value::parse allows you to pass utility::string_t or utility::istream_t, which on Windows are typedef'd to wstring and basic_stream<wchar_t> (wistream) and therefore utf-16 (also, per specification, the only valid encoding for JSON is utf-8)

Without jumping through hoops, it is practically impossible to receive a message from a websocket client and parse it as JSON.

[garethsb]

There are std::istream (UTF-8) overloads on Windows. It would make sense to me to add std::string overloads as well.

cpprestsdk/Release/include/cpprest/json.h

Lines 439 to 459 in b94bc32

	#ifdef _WIN32
	/// <summary>
	/// Parses a JSON value from the contents of a single-byte (UTF8) stream.
	/// </summary>
	/// <param name="stream">The stream to read the JSON value from</param>
	_ASYNCRTIMP static value __cdecl parse(std::istream& stream);
	/// <summary>
	/// Parses a JSON value from the contents of a single-byte (UTF8) stream.
	/// </summary>
	/// <param name="stream">The stream to read the JSON value from</param>
	/// <param name="errorCode">If parsing fails, the error code is greater than 0</param>
	/// <returns>The parsed object. Returns web::json::value::null if failed</returns>
	_ASYNCRTIMP static value __cdecl parse(std::istream& stream, std::error_code& error);
	/// <summary>
	/// Serializes the content of the value into a single-byte (UTF8) stream.
	/// </summary>
	/// <param name="stream">The stream that the JSON string representation should be written to.</param>
	_ASYNCRTIMP void serialize(std::ostream& stream) const;
	#endif

[garethsb]

Resolved by #1350 (in 2.10.16)?