message: Change cusomer param to required instead of optional
diff: @@ -59,7 +59,7 @@ pub struct InvoiceListLinesParams {
  }
  */
  -#[derive(Default, Serialize)]
  +#[derive(Debug, Default, Serialize)]
  pub struct InvoiceUpcomingParams<'a> {
  pub customer: &'a str, //this is a required param
  #[serde(skip_serializing_if = "Option::is_none")] pub coupon: Option<&'a str>,
  