This has two benefits:

• rollback won't get confused if the tag at registry.redhat.io/rhel9/postgresql-15:latest has moved to a new version between upgrade and rollback
• for airgapped scenarios where :latest maps to a specific SHA, upgrades and rollbacks will require that an administrator pull a SPECIFIC sha instead of just the latest, every time they upgrade to the version of postgresql-15 that was tested/shipped with a given RHDH version.

Note that digest pinning is already in place for the operator-bundle thanks to OSBS, but since OSBS has no concept of helm charts, we need to reinvent the same solution in https://gitlab.cee.redhat.com/rhidp/rhdh/-/blob/rhdh-1-rhel-9/build/helm/values_patch.yaml?ref_type=heads#L13 every time we push a new chart.