@type t() :: %PolarExpress.Schemas.DiscountFixedOnceForeverDurationBase{
  amount: integer() | nil,
  code: String.t() | nil,
  created_at: DateTime.t() | nil,
  currency: String.t() | nil,
  duration: PolarExpress.Schemas.DiscountDuration.t() | nil,
  ends_at: DateTime.t() | nil,
  id: String.t() | nil,
  max_redemptions: integer() | nil,
  metadata: PolarExpress.Schemas.MetadataOutputType.t() | nil,
  modified_at: DateTime.t() | nil,
  name: String.t() | nil,
  organization_id: String.t() | nil,
  redemptions_count: integer() | nil,
  starts_at: DateTime.t() | nil,
  type: PolarExpress.Schemas.DiscountType.t() | nil
}