Requests one or more invoice adjustments (refunds) in a single call, forwarded to
the AWS Marketplace BatchCreateBillingAdjustmentRequest API.

Entries succeed and fail independently. The response is 202 Accepted with
two parallel arrays: billingAdjustments for entries AWS accepted, and errors
for entries it rejected. Match each result to its request entry by clientToken.
A 202 with an empty billingAdjustments array means every entry failed. Inspect
errors before treating the call as successful.

Accepted entries start at PENDING. AWS takes up to 72 hours to move an entry to
COMPLETED or VALIDATION_FAILED. Poll the list endpoint or subscribe to the
agreement_billing_adjustment_updated webhook rather than blocking on the
response.

clientToken is the idempotency key and must be unique per entry, not per
request. Replaying a token returns the original result instead of creating a
second adjustment.

Each adjustmentAmount is an unsigned magnitude (e.g. "200.00"), matching
AWS Marketplace create and read — the resource type implies a credit. Its value
must not exceed that invoice's pricingCurrencyAmount.maxAdjustmentAmount.
currencyCode must match the invoice currency. AWS enforces both and reports
violations as per-entry VALIDATION_EXCEPTION errors, not as a request-level
400.