Function mz_storage_client::controller::persist_handles::append_work

async fn append_work<T2: Timestamp + Lattice + Codec64>(
    frontier_responses: &mut UnboundedSender<StorageResponse<T2>>,
    write_handles: &mut BTreeMap<GlobalId, WriteHandle<SourceData, (), T2, Diff>>,
    commands: BTreeMap<GlobalId, (Span, Vec<Update<T2>>, Antichain<T2>)>
) -> Result<(), Vec<GlobalId>>