message: Customers may not have a default source
diff: @@ -42,7 +42,7 @@ pub struct Customer {
  pub business_vat_id: Option<String>,
  pub created: u64,
  pub currency: Option<Currency>,
  - pub default_source: String,
  + pub default_source: Option<String>,
  pub delinquent: bool,
  pub desc: Option<String>,
  pub discount: Option<Discount>,
  