Document procedure to upgrade PostgreSQL chart image to 12.x
Document the processes to upgrade the version of PostgreSQL used by the
bitnami/postgresql chart, if deployed. Specifically, how to move from the current PG 11.x of the 4.x releases of these charts to that of PG 12.x, which will be added as an opt-in version in %13.4
As found in #1849 (closed), there is no method to automatically upgrade/downgrade the database files related to the
stable/postgresql chart's StatefulSet. As a result, a manual step is required to backup, reset, and restore the database in order to perform this upgrade.
We have done this previously, as seen in the upgrade instructions for 3.0.0 release. We can most likely reuse this script, and most of these steps.
Issue used when adding PG 11: #1956 (closed)