misc: update helm chart configs and readme (#1751)

* fix wiki helm

* update readme

* include service account as a stub

* use lightweight healthz for readiness and health endpoint

* remove if block for setting DB_TYPE, only postgres is supported in this chart for now

dev/helm/templates/tests/test-connection.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: "{{ include "wiki.fullname" . }}-test-connection"
+  labels:
+    {{- include "wiki.labels" . | nindent 4 }}
+  annotations:
+    "helm.sh/hook": test-success
+spec:
+  containers:
+    - name: wget
+      image: busybox
+      command: ['wget']
+      args: ['{{ include "wiki.fullname" . }}:{{ .Values.service.port }}']
+  restartPolicy: Never