add payment_method_details to Charge

[sherrardb]

my current reading of the docs and the response from post_charge() is that it is more robust to interrogate the payment_method_details than any individual card or source returned.

just wanted to capture this while the thought was fresh. more details to come.

[sherrardb]

i think that i'll address this when adding PaymentMethods/PaymentIntents, since i'm guessing that the mental context will be more conducive and the variety of different payment_method_details will be more apparent.