Function lk_linkpoint

pub fn lk_linkpoint(
    space: &dyn TryAsSpace,
    data: &[u8],
    links: &[Link],
) -> LkResult<PointBox>

create a new linkpoint PointBox

let datap = lk_datapoint(b"this is a datapoint")?;
let path = lkpath(&[b"hello",b"world"]);
let links = [
    Link{tag: ab(b"a datapoint"),ptr:datap.hash()},
    Link{tag: ab(b"another tag"),ptr:PUBLIC}
];
let data = b"extra data for the linkpoint";
let stamp = Some(U64::new(0)); // None == Some(now()).
let linkpoint = lk_linkpoint(data,b"mydomain",&links)?;

assert_eq!(linkpoint.hash().to_string(),"IdnnQjgxJLGxLZGKdaXWVxc82-U8KyJoyKK3sKlD8Lc");
assert_eq!(linkpoint.data(), data);
assert_eq!(*linkpoint.get_group(), PUBLIC);