Complete PG HA documentation

mentioned in issue #1807 (closed)

@ibaum Do you know if we plan to also provide documentation on how to deploy PG HA using Docker (either using plain Docker or inside k8s helm chart)?

@teemo I don't think there are any immediate plans for specific documentation. This documentation should be fairly platform agnostic. But it will be up to the user to recognize that a few of the steps won't work on their platform, and convert those to the appropriate step.

marked this issue as related to #2571

mentioned in issue #2831