Define use in postgres example

Author: jmckulk

kustomize/postgres/postgres.yaml

@@ -5,6 +5,10 @@ metadata:
 spec:
   image: registry.developers.crunchydata.com/crunchydata/crunchy-postgres:ubi8-16.3-1
   postgresVersion: 16
+  users:
+    - name: rhino
+      databases:
+        - zoo
   instances:
     - name: instance1
       dataVolumeClaimSpec: