message: let tests compile
diff: @@ -395,7 +395,7 @@ mod tests {
  let webhook = super::Webhook { current_timestamp: event_timestamp };
  let event = webhook
  - .do_construct_event(payload.to_string(), signature, secret)
  + .do_construct_event(payload, &signature, &secret)
  .expect("Failed to construct event");
  assert_eq!(event.event_type, super::EventType::InvoiceItemCreated);
  