Document Postgresql RDS and HA (in k8s) Options

[ranchodeluxe]

Most k8s projects with a DB do what we've already done here and spin it up as a pod with some resourcing options. But everyone knows for a production situation we'll want to think about failover, backups, availability.

The goal of this ticket is to:

• write up some documentation and examples about swapping in RDS
• explore what folks would need to do to run a high-availability cluster in k8s and document that also (https://portworx.com/blog/ha-postgresql-kubernetes/)

AC:

• write up some documentation and examples about swapping in RDS
• explore what folks would need to do to run a high-availability cluster in k8s and document that also

[emmanuelmathot]

to be added in #217