postgres replication

Warning

This change won't apply if bootstrap is done. In that case, old PVC will have an old password, and setting it through helm won't take effect. Deleting persistent volumes (PVs) will solve the issue. (mentioned here)

What does this MR do and why?

replication only occurs if number of control-planes >= 3 (if below, it will replicate but only 1 primary + 1 read replica)

• Adds replication spec in Helm Chart (1 primary + 3 read replicas)
• Adds PodDisruptionBudget (1 max unavailable)
• Adds PodAntiAffinity (1 read replicas per node max)

Related reference(s)

Ref #639 (closed)

Test coverage