Use the minimal PostgresOperator instead of the cas-postgres chart

[pbastia]

Using the postgres config as stated here: https://github.com/bcgov/how-to-workshops/blob/master/crunchydb/high-availablility/PostgresCluster.yaml

[LindsayMacfarlane]

Hi @pbastia - what is the priority for implementing this ticket?

[pbastia]

@LindsayMacfarlane I'd say low priority, I'll reclassify this as tech debt. The reason for doing this is that we want to stop maintaining the cas-postgres repo