feat(backoff): implement backoff when ApiError is called ?

[martintamare]

I think auto retry would be a nice feature.

What do you think about the following approach ?

It use backoff and by default has the same behavior as the old client. If someone would use auto_retry=4 in client init, if call would rise an APIError, it wall autoretry.

Tests are not done yet but will be, if you want it interesting.