Add support for link properties in derive macro

As far I can tell there's no way to use link properties in the derive macro currently, instead you need to map from `edged_protocol::Value` into the type you want in order to be able to use a type that contains a link. This is very unergonomic as most if not all the types we've been using thus far have some sort of link property that we want to access in Rust.

It would be nice if links were properly supported. I'd be happy to lend some time to help implementing this, but I would need guidance on how the decoding of links should work so I can generate the code in the `decode` implementation.

Start by tracing the derive macro's decode implementation and determine with maintainers how link properties should be decoded into Rust types. Done means the derive macro supports types containing links without manual mapping from edged_protocol::Value.

Written by the indexing model from the issue text.