Warn when the configuration is deprecated

[soupi]

What

We'd like to mark configuration version 3 and 4 as deprecated.
We'll mention this in the docs, and also trace a warning when starting the connector with an older configuration version.

{"timestamp":"2024-07-16T13:02:04.857565Z","level":"WARN","fields":{"message":"Warning: ndc-postgres configuration version '3' is deprecated.\nConsider upgrading to the latest version:\nhttps://hasura.io/docs/3.0/connectors/postgresql/configuration-reference/#upgrading-the-configuration-format-version"},"target":"ndc_postgres::connector"}

How

trace a warning pointing at how to upgrade the configuration.