Context:
We want to do a spike on if and how we could Elasticsearch 7.x and 6.x in parallel.

AT:

• identify relevant breaking changes https://www.elastic.co/guide/en/elasticsearch/reference/7.0/breaking-changes-7.0.html
• evaluation whether and how we can support both major versions at the same time
• once we know how we continue here inform our customer in SUPPORT-6780