A sales order item represents a single item on a sales order.
id - Integer - Unique id of the sales order item
product - Product - References the product
variant - Variant - References the variant
image - Image - The variant's primary image. If the variant has no primary image, the product's primary image is used.
price - Decimal - The per-unit price being paid for the item
quantity - Integer - The number of units being sold
total - Decimal - The price multiplied by the quantity
gsa_contract_number - String - The GSA contract number used if the customer is GSA and the product is being sold at a GSA price.