For developers: Discount criteria
  The discount criteria are used when creating discounts for selected users and/or roles. The criteria allow you to specify the ID of a user or role that the discount to be applied to. A discount can have more than one discount criteria set assigned to it.
 The discount criteria are represented by the Telerik.Sitefinity.Ecommerce.Orders.Model.DiscountCriteria class. The class exposes the following specific properties:
  - Parent
    Gets or sets the discount that the criteria set belongs to.  - RoleId
    Gets or sets the ID of the role for the criteria.  - UserId
    Gets or sets the ID of the user for the criteria.  
 NOTE: You must set either the RoleId or the UserId property of the DiscountCriteria instance. If you need to combine users and roles for the discount, create a discount criteria for each requirement.