Merge branch 'stable-3.0' into stable-3.1

* stable-3.0:
  Add support for Elasticsearch version 7.8.*

Change-Id: Id65b5b58c7e26312f93040d79a15696e50492ace
tree: 44fe9c8c17fb78a00ae0157643abda447a55c892
  1. java/
  2. javatests/