@type t() :: %PolarExpress.Schemas.BalanceCreditOrderMetadata{
  amount: integer() | nil,
  currency: String.t() | nil,
  fee: integer() | nil,
  order_id: String.t() | nil,
  product_id: String.t() | nil,
  subscription_id: String.t() | nil,
  tax_amount: integer() | nil,
  tax_country: String.t() | nil,
  tax_state: String.t() | nil
}