[BUG] Pay::Customer#customer no longer exists

[schristm]

Looks like the customer method used to access the payment processor's customer data is no longer available after this change:

1c1a5c1#diff-cd9fb0877977dacc88d88dac941f3cf5bd86d647c76c70c8138331e559f852fcL24

Documentation suggests it should still work:

https://github.com/pay-rails/pay/blob/main/docs/3_customers.md#retrieving-a-customer-object-from-the-payment-processor

Also tried api_record to no avail.

Thanks!