Added Helm chart for KillBill, Kaui, and MariaDB

[vnandwana]

• Added Helm chart for deploying KillBill, Kaui, and MariaDB on Kubernetes
• Added configurable images, replicas, services, and environment variables
• Configured Kubernetes service discovery between KB, Kaui, and MariaDB
• Added startup, readiness, and liveness probes
• Updated KB startup script to support configurable DB host
• Added Kubernetes service based communication between components

Ticket: https://github.com/killbill/technical-support/issues/252

[vnandwana]

Tested locally on Minikube

[sbrossie]

Things to address:

• Kaui Service points at the wrong port — helm/killbill/templates/kaui-service.yamlKaui listens on 8080 (containerPort: 8080), but the Service forwards to 9090:

• Kill Bill has no startupProbe — helm/killbill/templates/killbill-deployment.yaml

startupProbe:
  httpGet:
    path: /1.0/healthcheck
    port: 8080
  periodSeconds: 10
  failureThreshold: 60      # ~10 min to come up

• Are those really used: hpa.yaml and httproute.yaml - they seem disabled by default?

• Replace NOTES.txt with the real access path (current file is helm create scaffold that prints wrong commands):

Kill Bill and Kaui are starting. Give Kill Bill 1–3 min on first install.

kubectl port-forward svc/kaui {{ .Values.kaui.service.port }}:{{ .Values.kaui.service.port }}
# then open http://127.0.0.1:{{ .Values.kaui.service.port }}   (admin/password)

kubectl port-forward svc/killbill {{ .Values.killbill.service.port }}:{{ .Values.killbill.service.port }}
# Kill Bill API at http://127.0.0.1:{{ .Values.killbill.service.port }}

• Give MariaDB a volume so minikube stop/start and helm upgrade don't wipe the DB.