Skip PostgreSQL auto upgrade of HA nodes
Summary
Performing a PostgreSQL upgrade on HA nodes requires some manual steps. In 12.10, we will default to PostgreSQL 11 for new installs, and will auto upgrade existing installs unless they have HA or Geo configured.
The work to skip auto upgrades for Geo is being addressed in #5251 (closed).
Proposal
This issue is to use existing tooling that detects whether repmgr is in use, and add logic that skips auto upgrades when repmgr is detected. It should also include any necessary modifications to existing messaging to advise HA customers that they need to manually upgrade, and updates to documentation to ensure that the upgrade experience is clear.
Single node installs and multi node installs not using HA or Geo will automatically upgrade to PosgtreSQL 11 in 12.10.