Datagraph item on the API doesn't expose enough information

[Southclaws]

Currently, "Datagraph items" represent a generic shape of either thread/reply/post, profile, library page, and probably more eventually. The point of a "Datagraph item" abstraction is to provide a generic data structure for contexts where mixing content types makes sense. Search results being the main one, as well as recommendations ("you like this post, you may like this stuff [post, profile, post, post, page]")

Right now the data is:

    "items": [
        {
            "assets": null,
            "description": "Search",
            "id": "crsj1rqfunp46b6u1hs0",
            "kind": "post",
            "name": "Search",
            "slug": "crsj1rqfunp46b6u1hs0-search"
        }
    ],

Which isn't enough, we also need to expose:

• primary image (for posts, it's either the first image in the content, or the preview image of the first link... maybe, for links it's just the opengraph image "primary_image", for library pages it's the upcoming "primary_image", for profiles it's the avatar)
• content: for posts/pages/etc the actual HTML content, for profiles it's the bio, for links it's the extracted content description
• author: everything has an author so we need to expose it as a ProfileReference for proper rendering
• created date: obvious

future stuff:

• tags
• category? only applies to posts, but worth exposing I guess
• recommendations? may get expensive