Context:
There's a lot of documentation about how Optimize can connect to a secured Elasticsearch instance which is related to the old Elasticsearch version 6.0-6.2:
https://docs.camunda.org/optimize/latest/technical-guide/setup/secure-elasticsearch/

With Optimize 3.0.0 we use Elasticsearch 7.X and with this version, x-pack is part of the distro by default and there's no need to install it any longer. Also, there's no clear recommendation of the Elasticsearch permissions the Optimize Elasticsearch user should have.

AT:

• the documentation about how to connect Optimize to Elasticsearch 7.X is up-to-date
• there's a recommendation which kind of role and permissions the Optimize Elasticsearch user needs
• the adjustments are backported to the version 3.0 in the docs
• there's a test running to ensure that Optimize just needs the recommended permission/role settings stated in the documentation