fn fetch_auth<Fetch, Fut, Pdu>( id: usize, event_id: OwnedEventId, fetch: &Fetch, ) -> impl Future<Output = (usize, OwnedEventId, Result<Pdu>)> + Sendwhere Fetch: Fn(OwnedEventId) -> Fut, Fut: Future<Output = Result<Pdu>> + Send,