JSON Patch request for incremental ERP sync. Send If-Match with the document etag.
Typical integration updates: /amount, /remainingAmount, /glEntries, /appliedDocuments,
/voided, /description, /reference, /references, /date, /issueDate, /counterparty, and /currencyExchange.
/reconciliationStatus and /reconciliationMatchId mirror reconciliation state; prefer letting reconciliation update them when possible.