Map ERP data

Every CFO row must trace back to a stable ERP document or line without putting PII or secrets in its identity.

CFO field	Mapping rule
external_ref	Stable document/line business identity; unchanged on retry
external_batch_id	Submission batch identity saved before the network call
Idempotency-Key	Transport identity for one canonical request
document_date	YYYY-MM-DD inside the selected reporting period
activity_code	Value returned by capability discovery
catalog_item_code	Item paired with that discovered activity
quantity	Positive ERP amount that does not round to zero
unit	Exact accepted unit from discovery

Some Scope 3 transport items accept direct tkm; others may support weight_kg with distance_km. Follow the discovered contract. Do not calculate or hard-code emission factors in the ERP—CFO resolves the factor and returns the calculation version.

Canonicalize and hash the payload before sending so a restart can prove that the exact request was retried.