fix: Update Klarna and Afterpay payment source parameters

fix: Update Klarna and Afterpay payment source parameters: a task in bird-critic-1.5-full-300 (Harbor dataset). The Shopware PayPal SDK models PayPal's V2 Order API payment source structs. The Klarna and Afterpay payment source structs used flat scalar fields for the customer name and lacked…

The task

The Shopware PayPal SDK models PayPal's V2 Order API payment source structs. The `Klarna` and `Afterpay` payment source structs used flat scalar fields for the customer name and lacked support for billing addresses and Klarna-specific context objects. This update aligns the structs with the current PayPal API schema.

Part of kochsnow/bird-critic-1.5-full-300.