@type t() :: %Polarex.CustomerStateSubscription{
  amount: integer(),
  cancel_at_period_end: boolean(),
  canceled_at: DateTime.t() | nil,
  created_at: DateTime.t(),
  currency: String.t(),
  current_period_end: DateTime.t(),
  current_period_start: DateTime.t(),
  custom_field_data: map() | nil,
  discount_id: String.t() | nil,
  ends_at: DateTime.t() | nil,
  id: String.t(),
  metadata: map(),
  meters: [Polarex.CustomerStateSubscriptionMeter.t()],
  modified_at: DateTime.t() | nil,
  product_id: String.t(),
  recurring_interval: String.t(),
  started_at: DateTime.t() | nil,
  status: String.t(),
  trial_end: DateTime.t() | nil,
  trial_start: DateTime.t() | nil
}