Sep31Refund Payment
Single on-chain refund payment within a SEP-31 Sep31Refunds aggregate.
Each instance describes one Stellar transaction the Receiving Anchor used to send funds back to the Sending Anchor. Multiple refund payments may exist for a single SEP-31 transaction; the aggregate is captured in Sep31Refunds.
The amount and fee fields are String (not numeric) because SEP-31 amounts must preserve decimal precision; callers convert to a domain-specific numeric type at the application boundary.