Missing functionality for automated chargeback handling (v1 vs v2)

Following the integration guide on handling IPN notifications:
https://amazonpaycheckoutintegrationguide.s3.amazonaws.com/amazon-pay-checkout/set-up-instant-payment-notifications.html#ipn-types

Chargeback notification can be initiated, but the only way to handle it is:
> Look up chargeback details in Seller Central using the chargePermissionId

This is inconsistent with v1 API, where chargeback information was normally included in IPN.

Therefore I believe that chargeback object get method is clearly missing in v2 API.

Start with the linked Amazon Pay IPN integration guide, then compare the v1 chargeback handling with the v2 SDK's existing notification and chargeback-related entry points. Done means v2 provides a chargeback-details retrieval path so chargeback notifications can be handled without looking up details manually in Seller Central.

Written by the indexing model from the issue text.