hack/setup_external_dev_services: Improve postgresql installation

The postgresql helm chart requires the cluster to provide a PersistentVolume
and places a PersisentVolumeClaim for this.
Ensure that the cluster provides PersistentVolumes.

Also set volumePermissions.enabled=true which helps to fix Permission denied
when trying to create the data directory in the PV mount directory
if the PV's permissions are not open enough:
https://github.com/bitnami/charts/issues/1210#issuecomment-1145923630

hack/setup_external_dev_services

@@ -31,9 +31,46 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
+# TODO: Setup an bash error trap, to make errors from failing commands more
+# visible and draw attention of the user to these errors.
+
 # Install postgres
 helm repo add bitnami https://charts.bitnami.com/bitnami
-helm upgrade --install postgres bitnami/postgresql --set global.postgresql.auth.postgresPassword=postgres --set auth.postgresPassword=postgres --set auth.enablePostgresUser=true
+
+# Documentation and source of the used chart with all configuration parameters:
+# https://artifacthub.io/packages/helm/bitnami/postgresql
+# https://github.com/helm/charts/tree/master/stable/postgresql
+
+# The postgresql helm chart requires the cluster to provide a PersistentVolume
+# and places a PersisentVolumeClaim for this.
+# Ensure that the cluster provides PersistentVolumes:
+
+if kubectl get PersistentVolume -o json
+   | jq -e '.items | .[].status | select(.phase == "Bound")' ; then
+    echo "Ok found at least one PersistentVolume"
+else
+    echo "The postgresql helm chart has a PersistentVolumeClaim (PVC)."
+    echo "The cluster needs to provide at one PersistentVolume (PV) for this."
+    echo "For information how to create a PersistentVolume, see:"
+    echo "https://github.com/felipecruz91/k8s-postgresql-persistent-volume#create-persistent-volume"
+    exit 5
+fi
+
+# Note: The chart mounts the PV at persistence.mountPath,
+# which defaults to /bitnami/postgresql and creates a directory /data in it.
+# If it has no permission to create it, this error happens:
+# mkdir: cannot create directory ‘/bitnami/postgresql/data’: Permission denied
+# https://github.com/bitnami/charts/issues/1210
+#
+# Adding --set volumePermissions.enabled=true helps:
+# https://github.com/bitnami/charts/issues/1210#issuecomment-1145923630
+
+helm upgrade --install postgres bitnami/postgresql                  \
+             --set volumePermissions.enabled=true                   \
+             --set global.postgresql.auth.postgresPassword=postgres \
+             --set auth.postgresPassword=postgres                   \
+             --set auth.enablePostgresUser=true                     \
+
 kubectl patch svc postgres-postgresql --type='json' -p '[{"op":"replace","path":"/spec/type","value":"NodePort"}]'
 
 # Install localstack