PATCH update — all fields optional. Only fields explicitly sent are written; everything else stays as-is on the row.

Cross-field invariants that depend on a complete picture (zip half-set, destination hierarchy) run in the service against the merged row — not against the patch alone, since a partial patch legitimately omits fields the row already has set. The schema only catches errors visible inside the patch itself (zip range ordering

• length, effective-date ordering, both when both ends are sent).