* [cpp-restsdk] add support for oneOf via std::variant
* [cpp-restsdk] detect the latest supported C++ standard in CMake
* [cpp-restsdk] add test with oneOf support for cpprest
* [cpp-restsdk] avoid warnings because of implicit this capture
* [cpp-restsdk] avoid deprecated CMake version warnings
* [cpp-restsdk] build the test into the build directory - parallel build
* [cpprest-sdk] use absolute source path for cmake + debug build
* fix: remove inheritance due to template not overriding
---------
Co-authored-by: William Cheng <wing328hk@gmail.com>