@type t() :: %PolarExpress.Schemas.CheckoutUpdatePublic{
  allow_trial: boolean() | nil,
  amount: integer() | nil,
  custom_field_data:
    %{
      required(String.t()) =>
        String.t() | integer() | boolean() | DateTime.t() | nil
    }
    | nil,
  customer_billing_address: PolarExpress.Schemas.AddressInput.t() | nil,
  customer_billing_name: String.t() | nil,
  customer_email: String.t() | nil,
  customer_name: String.t() | nil,
  customer_tax_id: String.t() | nil,
  discount_code: String.t() | nil,
  is_business_customer: boolean() | nil,
  locale: String.t() | nil,
  product_id: String.t() | nil,
  product_price_id: String.t() | nil,
  seats: integer() | nil
}