Define supported Postgres versions for Postgres Plugin

[dylanlott]

We currently do not have a minimum supported version defined for the Postgres plugin. We should define a minimum and preferred Postgres version, and be explicit about what operation modes are supported in which versions.

[devarismeroxa]

What is the minimum version that can have CDC enabled either native or via a plugin? That would be my starting point @dylanlott

[neovintage]

I'd start with what most cloud providers are choosing to support. For example, AWS RDS is about to deprecate 9.6. This means 10 will be the oldest supported version.

[dylanlott]

@devarismeroxa I believe version 9.4 introduced access to the WAL, which enabled CDC features.
Supporting what most other cloud providers are supporting makes sense to me, though, especially if we don't have a specific need for an older version.

[dylanlott]

Postgres versioning has 10.19 as the latest minor version of 10 and it has a scheduled final release of 10 Nov 2022. If we pick 10, my thought would be latest minor version of 10, but I'm open to other ideas.

For additional context, the final release for a 9.X version was 21 Nov 2021.

[neovintage]

@dylanlott v10 sounds reasonable to me. If there are a ton of requests for lower versions we could revisit.

[dylanlott]

@neovintage I'm going to update the documentation to reflect this version choice then. 👍