Include basic liveness & readiness probes

[bmm-alc]

(taking the same text than the previous PR)

Include a HTTPS request to the root path (/) that returns a 200 OK and does not require a token to be requested.

This is important because, if the lighttpd server dies, the container keeps running and K8s never notices. You can reproduce this behavior by entering the container (e.g. kubectl exec -it xxxxx sh) and sending a kill -9 to the lighttpd process.

With this change, kubernetes notices the pod is no longer live > kill it > relaunch it and everything keeps running.

patch from https://github.com/WhatsApp/WhatsApp-Business-API-Setup-Scripts/pull/48

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[Goodsmileduck]

Hi, won't it better to add something with Auth and request /v1/health instead? Like

        livenessProbe:
          exec:
            command:
            - 'bash'
            - '-c'
            - 'curl --fail -k https://localhost:443/v1/health --header "Authorization: Apikey ${WA_API_KEY}"'
          initialDelaySeconds: 30
          periodSeconds: 15
...
        env:
        - name: WA_API_KEY
          valueFrom:
            secretKeyRef:
              name: some_wa_secret
              key: WA_API_KEY
...

You can generate api key and put it into secret some_wa_secret and value like WA_API_KEY: base64 secret

secret also could be autogenerated in _helpers if using helm chart:

{{- define "livenessProbeToken" -}}
{{- $token := (lookup "v1" "Secret" .Release.Namespace .Values.tokenSecretName ) -}}
{{- if $token -}}
{{- $token.data.WA_API_KEY -}}
{{- else -}}
{{- randAlpha 20 | b64enc -}}
{{- end -}}
{{- end -}}

and then secret yaml

---
apiVersion: v1
kind: Secret
metadata:
  name: some_wa_secret
data:
  WA_API_KEY: {{ template "livenessProbeToken" . }}