No chargily_pay_fees_allocation in the Checkout class

[HoussemCoder]

Hi
I found in the Checkout docs that pass_fees_to_customer is deprecated and we should use chargily_pay_fees_allocation instead, but I didn't find that attr in the Checkout class in entity.py.

I have created a pull request for that too.

Note: I found a lot of attrs in the docs not found in the Checkout class!!