The request body is a flat array of package objects — not wrapped in a parent object. The purchase order must be in IN_PROGRESS status and owned by the requesting user.

quantity and to_par

Each package entry must provide either quantity or to_par, but not both:

• quantity — the number of units to order. Must be a non-negative number. Sending 0 removes the package from the order if it was already present.
• to_par — when true, the quantity is automatically calculated as par − (current stock + outstanding orders), rounded up. If stock already meets or exceeds par, the calculated quantity is 0 and the package is removed from the order if it was already present.