Function for_each_diff_pair_async 

pub async fn for_each_diff_pair_async<B, C, F, E>(
    batch: &B,
    lower: Option<Antichain<C::Time>>,
    upper: Option<Antichain<C::Time>>,
    on_diff_pair: F,
) -> Result<(), E>
where
    B: BatchReader<Time = C::Time> + Navigable<Cursor = C>,
    C: Cursor<Storage = B, Diff = Diff>,
    C::Time: Copy,
    C::ValOwn: 'static,
    F: AsyncFnMut(&<C::KeyContainer as BatchContainer>::Owned, C::Time, DiffPair<C::ValOwn>) -> Result<(), E>,

Just like for_each_diff_pair, but async and fallible.

Thin wrapper around iter_diff_pairs.