According to the spec, sending a link should look like this:

{
    "posts": {
        "id": "2",
        "title": "How to fry an egg",
        "links": {
            "author": {
                "href": "/users/5"
            }
        }
    }
}

The formatter is currently sending:

{
    "posts": {
        "id": "2",
        "title": "How to fry an egg",
        "links": {
            "author": "/users/5"
        }
    }
}

There is no way for the client to tell that that is a link and not an ID. This PR changes the handling for [SerializeAs(SerializeAsOptions.Link)] to put the link on an href key in an embedded object.

I needed the json minifier helper from #8, so I included it here as a separate commit. I may need to rebase one of these PRs when you merge the other.