Update  /users/ invite_user cmd to use invite_user call instead of create_user 

See [this](https://github.com/ryran/python-sdk/commit/a6c62d1ab6d10d865b81f6936599c97a5ce1faba) and [this](https://github.com/ryran/python-sdk/commit/3814ca65e59761d1604a8fcb00371d13707c1b5c)