Provide a resource identifier instead of omitting the resource when access is denied

This is an spin-off of #2943176-13: Spec Compliance: when error object 'id' key exists, it contains the individual resource URI, instead of "a unique identifier for this particular occurrence of the problem".

In order to provide more useful errors when access is denied to a resource, we would like to be able to have a source.pointer key in the error object which references the resource identifier for the restricted resource.

That would look something like this:

{
  "data": [
    {"type": "node--accessible", "uuid": "some-random-uuid", "attributes": {...}, "relationships": {...}},
    {"type": "node--inaccessible", "uuid": "some-random-uuid"}
  ],
  "meta": {
    "errors": [
      {
        "status": 403,
        "title": "Access Denied",
        "source": {
          "pointer": "/data/1"
        }
      }
    ]
  }
}

This will also improve DX with regard to pagination because responses will no longer contain fewer items than the page limit, even when sufficient resources exist to "fill" the page.

To do this, we must stop omitting restricted resources entirely and include only a resource identifier.