t() :: %Thinkific.Model.PromotionRequest{
  amount: float(),
  coupon_ids: [float()],
  description: String.t(),
  discount_type: DiscountType,
  duration: float(),
  expires_at: DateTime.t(),
  name: String.t(),
  product_ids: [float()],
  starts_at: DateTime.t()
}