MST and repository parsing APIs about atrium HOT 3 OPEN

struct Repository<R: tokio::io::AsyncRead + tokio::io::AsyncSeek> { .. }

impl<R: AsyncRead + AsyncSeek + Unpin + Send> Repository<R> {
    async fn load(reader: R) -> Result<Self, _> { .. }

    fn did(&self) -> &Did { .. }
    fn keys<'a>(&'a mut self) -> impl Stream<Item = Result<String, _>> + 'a { .. }

    fn get_collection<'a, C: Collection + 'a>(
        &'a mut self,
    ) -> impl futures::Stream<Item = Result<(RecordKey, C::Record), _>> + 'a { .. }

    fn get_collection_reversed<'a, C: Collection + 'a>(
        &'a mut self,
    ) -> impl futures::Stream<Item = Result<(RecordKey, C::Record), _>> + 'a { .. }

    async fn get<C: Collection>(
        &mut self,
        rkey: &RecordKey,
    ) -> Result<Option<C::Record>, _> { .. }
}

mod mst {
    enum Located<E> {
        Entry(E),
        InSubtree(Cid),
    }

    struct Node { .. }

    impl Node {
        fn parse(bytes: &[u8]) -> Result<Option<Self>, _> { .. }
        fn get(&self, key: &[u8]) -> Option<Located<Cid>> { .. }

        fn entries_with_prefix<'a>(
            &'a self,
            prefix: &'a [u8],
        ) -> impl Iterator<Item = Located<(&[u8], Cid)>> + 'a { .. }

        fn reversed_entries_with_prefix<'a>(
            &'a self,
            prefix: &'a [u8],
        ) -> impl Iterator<Item = Located<(&[u8], Cid)>> + 'a { .. }
    }
}