Taking them by const reference isn't advisable here, because it means
the std::move calls were doing nothing and we were always copying the
std::string instances.
* Change authentication system to JWT
* Address review comments
* Get rid of global variable, fix some documentations, fix a bug when verificating
* Refactor PostJson to avoid code duplication
* Rename jwt_token, add functionality to request a new JWT when getting a 401
* Take bools by value instead of const reference
* Send request again when JWT is invalid and use forward declarations
* Omit brackets
