This project contains container images shared across the Percona Distribution for
PostgreSQL major versions that ship the "extras" package set (currently 16-18), such as
the custom major-version upgrade image that bundles those extra extensions. It is not tied
to a single staging/, so its released counterpart is ppg:releases:extras:containers
rather than a per-version releases//extras subproject.
We currently build these images based on UBI-9 only, matching the per-version
extras/containers projects (there is no UBI-8 variant of the extras/custom images).