impl FCMError {
  fn from_status(status: &StatusCode, body: typeof Body) -> Self {
    match status {
      StatusCode::BAD_REQUEST => FCMError(Unavailable),
      StatusCode::NOT_FOUND => FCMError(Unregistered),
      // ...
      _ => FCMError(UnspecifiedError)
    }
  }
}

match response.status() {
    StatusCode::OK => {
      debug!("Successfully sent FCM notif to {}", token);
      Ok(())
    }
    error_status => {
      let body = response.text().await.unwrap();
      error!(
        "Failed sending FCM notification to: {}. Status: {}. Body: {}",
        token, error_status, body
      );
      let fcm_error = FCMError::from_status(error_status, body);
      Err(fcm_error)
    }