2025
Otus - What is New in ES and OpenSearch for 4 years of 1:14:52
    https://www.youtube.com/watch?v=vbBO3ssXw0Q
    ! so-so
7.x
https://www.elastic.co/guide/en/elasticsearch/reference/7.0/breaking-changes-7.0.html
6.x
https://www.elastic.co/blog/elastic-stack-6-7-0-released
    https://www.elastic.co/blog/elasticsearch-6-7-0-released
    https://www.elastic.co/blog/kibana-6-7-0-released