Set of purchase item types for which rule applies. If nothing is specified, the rule will be apply to all options.
Currently the following are supported: 'DIGITAL_PRODUCT', 'DIGITAL_PRODUCT_RENTAL', 'ELECTRICITY', 'ELECTRICITY_RESALE',
'LABOR_COST', 'LOGISTIC_COST', 'PHYSICAL_PRODUCT', 'PHYSICAL_PRODUCT_RENTAL', 'SERVICE', 'VOUCHER'.