The purchase order must be in IN_PROGRESS status and owned by the requesting user.

supplier_email_input

Only required when the supplier has no configured email address and supports email orders. When the supplier already has one or more configured email addresses, this field is ignored and the order is sent to those addresses.

expected_delivery_date

Must not be in the past. If the outlet has an ordering schedule configured for this supplier, the date must also comply with that schedule — requests that fall outside the supplier's delivery days or past the order cutoff time will be rejected.