The external purchase object describes an external purchase that can be part of an order.
| Field name | Type | Description |
|---|---|---|
| title | I18N | The title of the external purchase to be printed on the invoice. |
| product_reference | String | A reference to a product for an external purchase. |
| unit_price | Amount | The price of a unit that comprise an external purchase. |
| quantity | Number | The number of units that comprise an external purchase. |