Include configuration of an external Elasticsearch

[jonathanlukas]

As we recommend externalizing Elasticsearch, we should offer a guide on how to do this.

Important aspects are:

• TLS configuration (including a self-signed cert)
• Credentials
• varying prefixes to allow parallel usage of multiple clusters

[ManuelDittmar]

Hi @jonathanlukas, do you think https://github.com/camunda/camunda-platform-helm/issues/473 is sufficient? I think the configuration will be easier with the 8.3 release

[jonathanlukas]

Interesting issue. However, we should have this as a topic (without the elasicsearch itself, I like the idea of using elastic cloud as an example)

Idea: Maybe this could be part of a chapter about externalising components (which would include keycloak, elasticsearch and database(s))