fn auth_chain_ids<'a, F>(
services: &'a Services,
chain: F,
) -> impl Stream<Item = OwnedEventId> + Send + 'awhere
F: Future + Send + 'a,
F::Output: IntoIterator<Item = ShortEventId> + Send + 'a,
<F::Output as IntoIterator>::IntoIter: Send + 'a,