Include links.related

How do I include `links.related` for every relationship?

The same for every compound document

What I'm referring to is something like:

```
"attributes": {
  ...
},
"relationships": {
  "comments": {
    "links": {
      "related": "http://localhost/api/v1/users/1/comments"
    },
    "data": {
      "type": "comments",
      "id": 115
    }
},
```