Add endpoint for getting credits informations

[gbnk0]

like {"credits": 140}

[JouseJG]

I have created a pull request with that same endpoint, I have called it "get_credits" and you don't need to pass any data for body or Query. The call pulls more data from the user but I have limited it to these fields:
-credits_left
-period
-monthly_limit
-monthly_usage

Anyway as of this writing I have not been approved yet so if you want to try the endpoint you can try my Fork