Full prescription edit. Pre-Dispensed prescriptions are updated in place; Dispensed prescriptions require a `reason` and the change is recorded as an amendment. DEA-tracked field changes on a controlled substance are blocked — caller must cancel-and-recreate instead.

Required for post-Dispensed amendments; ignored otherwise.

Patient's last exam date (VCPR - Veterinary-Client-Patient Relationship)

Set when the dispense-from-inventory call included an InvoiceId and a line item was created atomically with the dispense. Lets clients append the line item locally without refetching.

The estimate the dispense was attached to — either the one the caller supplied or one auto-created/resolved server-side. Lets a client that had no estimate of its own adopt the server's estimate instead of failing to reconcile the line.

ISO date string (YYYY-MM-DD).