message: added default to refund params
diff: @@ -73,7 +73,7 @@ pub enum RefundFailureReason {
  /// The set of parameters that can be used when creating refund object.
  ///
  /// For more details see [https://stripe.com/docs/api/refunds/create](https://stripe.com/docs/api/refunds/create).
  -#[derive(Clone, Debug, Deserialize, Serialize)]
  +#[derive(Clone, Debug, Default, Deserialize, Serialize)]
  pub struct RefundParams {
  pub charge: String,
  pub amount: Option<u64>,
  