How to use "track_scores": true on TopHitsAggregation ?

[Ikaer]

NEST/Elasticsearch.Net version: 5.5.0

Elasticsearch version: 5.5.2

Description of the problem including expected versus actual behavior:
Hello, I need to compute scores on a sorted top hit aggregation by setting the "track_scores" property to true.
But I cannot found how to do that with NEST. "track_score" is available in the SearchRequest class but not in TopHitsAggregations

Steps to reproduce:

1. This is a simplified version of what I'm trying to achieve with the API:

GET myIndex/myType/_search
{
	"from": 0,
	"size": 1,
	"_source": false,
	"query": {
		"match_all": {}
	},
	"aggs": {
      "top_hits": {
			"top_hits": {
				"size": 20,
				"track_scores": true,
				"_source": false,
				"sort": [{
					"skus._order.BestSkuRule": {
						"order": "asc"
					}
				}]
				}
			}
		}
	}
}

The query is working and and the_score property is filled in top hits aggregation:

{
  "took": 1,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "failed": 0
  },
  "hits": {
    "total": 1604,
    "max_score": 1,
    "hits": [
      {
        "_index": "myIndex",
        "_type": "myType",
        "_id": "10522_17385",
        "_score": 1
      }
    ]
  },
  "aggregations": {
    "top_hits": {
      "hits": {
        "total": 1604,
        "max_score": 1,
        "hits": [
          {
            "_index": "myIndex",
            "_type": "myType",
            "_id": "10522_39993",
            "_score": 1,
            "sort": [
              1
            ]
          }
        ]
      }
    }
  }
}

But with NEST I cannot set "track_scores" to true so scores are null:
Query generated with NEST:

GET myIndex/myType/_search
{
	"from": 0,
	"size": 1,
	"_source": false,
	"query": {
		"match_all": {}
	},
	"aggs": {
      "top_hits": {
			"top_hits": {
				"size": 20,
				"_source": false,
				"sort": [{
					"skus._order.BestSkuRule": {
						"order": "asc"
					}
				}]
				}
			}
		}
	}
}

results:

{
  "took": 1,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "failed": 0
  },
  "hits": {
    "total": 1604,
    "max_score": 1,
    "hits": [
      {
        "_index": "myIndex",
        "_type": "myType",
        "_id": "10522_17385",
        "_score": 1
      }
    ]
  },
  "aggregations": {
    "top_hits": {
      "hits": {
        "total": 1604,
        "max_score": null,
        "hits": [
          {
            "_index": "myIndex",
            "_type": "myType",
            "_id": "10522_39993",
            "_score": null,
            "sort": [
              1
            ]
          }
        ]
      }
    }
  }
}

Am I missing something ? Thanks in advance for your time.

[Mpdreamz]

This is blatantly missing, opened #2846 to add it in and will make it in the next release. Thanks for making us aware @lkaer