@type t() :: %BexioApiClient.Purchase.BillDiscount{
  amount: float(),
  id: String.t() | nil,
  position: non_neg_integer()
}

Discount of a bill in purchase.

Fields:

• :id - id of the discount, nil for new discounts in update requests
• :position - position of the discount
• :amount - amount of the discount, must be greater than 0 and less than the line items total