ES aggregation by multiple terms

Please add a Junit test that will query the ES for count(species), aggregated by genus, species -- an aggregation of species within genus. See https://www.elastic.co/guide/en/elasticsearch/reference/6.8/search-aggregations-bucket-terms-aggregation.html

Use JUnit to print ES query and then apply it to your indexed ES.

GET /_search
{
    "aggs" : {
        "genus" : {
            "terms" : {
                "field" : "genus",
                // "order" : { "playback_stats.max" : "desc" }
            },
            "aggs" : {
                // "playback_stats" : { "stats" : { "field" : "play_count" } }
                "species": { "terms": { "field": "species" } },
                "aggs" : {
                 // "playback_stats" : { "stats" : { "field" : "play_count" } }
                   "origin.iso3166": { "terms": { "field": "origin.iso3166" } }
                }
            }
        }
    }
}

The result should be something like:

genus	species	count
Arabidopsis	Arabidopsis thaliana	686,602
Hordeum	Hordeum vulgare	235,395
Hordeum	Hordeum Hordeum vulgare	17,788
Hordeum	...	.
Triticum	Triticum aestivum	332,060
Triticum	Triticum turgidum	73,364
Triticum	Triticum triticum aestivum	29,196

How can we control the number of results?

For genesys-ui#782