@type t() :: %PolarExpress.Schemas.CustomerUpdatedFields{
  billing_address: PolarExpress.Schemas.AddressDict.t() | nil,
  email: String.t() | nil,
  metadata:
    %{required(String.t()) => String.t() | integer() | boolean() | nil} | nil,
  name: String.t() | nil,
  tax_id: String.t() | nil
}