OrderItem: OrderItem
In cboettig/schemar: Create Structured Data Using the Schema.org Vocabulary

An order item is a line of an order. It includes the quantity and shipping details of a bought offer.

OrderItem(id = NULL, orderedItem = NULL, orderQuantity = NULL,
  orderItemStatus = NULL, orderItemNumber = NULL, orderDelivery = NULL,
  url = NULL, sameAs = NULL, potentialAction = NULL, name = NULL,
  mainEntityOfPage = NULL, image = NULL, identifier = NULL,
  disambiguatingDescription = NULL, description = NULL,
  alternateName = NULL, additionalType = NULL)

`id`	identifier for the object (URI)
`orderedItem`	(Product or OrderItem or Product or OrderItem type.) The item ordered.
`orderQuantity`	(Number type.) The number of the item ordered. If the property is not set, assume the quantity is one.
`orderItemStatus`	(OrderStatus type.) The current status of the order item.
`orderItemNumber`	(Text type.) The identifier of the order item.
`orderDelivery`	(ParcelDelivery or ParcelDelivery type.) The delivery of the parcel related to this order or order item.
`url`	(URL type.) URL of the item.
`sameAs`	(URL type.) URL of a reference Web page that unambiguously indicates the item's identity. E.g. the URL of the item's Wikipedia page, Wikidata entry, or official website.
`potentialAction`	(Action type.) Indicates a potential Action, which describes an idealized action in which this thing would play an 'object' role.
`name`	(Text type.) The name of the item.
`mainEntityOfPage`	(URL or CreativeWork type.) Indicates a page (or other CreativeWork) for which this thing is the main entity being described. See [background notes](/docs/datamodel.html#mainEntityBackground) for details.
`image`	(URL or ImageObject type.) An image of the item. This can be a [[URL]] or a fully described [[ImageObject]].
`identifier`	(URL or Text or PropertyValue type.) The identifier property represents any kind of identifier for any kind of [[Thing]], such as ISBNs, GTIN codes, UUIDs etc. Schema.org provides dedicated properties for representing many of these, either as textual strings or as URL (URI) links. See [background notes](/docs/datamodel.html#identifierBg) for more details.
`disambiguatingDescription`	(Text type.) A sub property of description. A short description of the item used to disambiguate from other, similar items. Information from other properties (in particular, name) may be necessary for the description to be useful for disambiguation.
`description`	(Text type.) A description of the item.
`alternateName`	(Text type.) An alias for the item.
`additionalType`	(URL type.) An additional type for the item, typically used for adding more specific types from external vocabularies in microdata syntax. This is a relationship between something and a class that the thing is in. In RDFa syntax, it is better to use the native RDFa syntax - the 'typeof' attribute - for multiple types. Schema.org tools may have only weaker understanding of extra types, in particular those defined externally.