https://access.redhat.com/documentation/en-us/red_hat_quay/3.4/html-single/deploy_red_hat_quay_for_proof-of-concept_non-production_purposes/index#setting_up_postgres

We promote the usage of a docker.io image here when what we should be using is the official RHEL8 version of Postgres: https://catalog.redhat.com/software/containers/rhel8/postgresql-12/5db133bd5a13461646df330b

Because of this different image all the proposed environment variables need to change as well (POSTGRES_USER vs. POSTGRESQL_USER)