Like with TelemetryJson, we can make the implementation details private
and avoid the need to expose httplib to external libraries that need to
use the Client class.
* 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
* WebService: Verify username and token; Log errors in PostJson
* Fixup: added docstrings to the functions
* Webservice: Added Icons to the verification, imrpved error detection in cpr, fixup nits
* fixup: fmt warning
