impl From<PaMap> for OwnedPathAttributes

[density215]

While trying to write tests best path selection in rotonda-store - which requires From<Vec<u8>> and Into<Vec<u8>> for types to be stored - I need a way to create OwnedPathAttributes from scratch (so not from an existing PDUs). One way could be to create an empty PaMap and try to convert that into a PathAttributes.

I though a (convoluted) way could be:

OwnedPathAttributes::from((
    PduParseInfo::modern(),
    UpdateBuilder::<Vec<u8>>, Ipv4UnicastNlri>::from_attributes_builder(pa_map)
        .into_pdu_iter(&SessionConfig::modern())
        .next()
        .unwrap()
        .unwrap()
        .octets()
        .to_vec(),
));

This is incorrect, however.

Having an From<..> impl for this, would allow OrdRoute to take &OwnedPathAttributes as argument, instead of &PaMap. This would be handy, since Rotonda itself stores OwnedPathAttributes as its meta type in the store.

[DRiKE]

This raises some nice points for the ongoing refactor of the path attributes, which we'll need to discuss a bit more, but for now maybe this can get things going:

let mut pamap = PaMap::empty();
pamap.set(crate::bgp::types::Origin(OriginType::Igp));
let mut buf = Vec::new();
for pa in pamap.attributes.values() {
    pa.compose(&mut buf).unwrap();
}
let owned = OwnedPathAttributes::from((PduParseInfo::modern(), buf));