Add the proposal about the helm chart autogenerate plugin.

Signed-off-by: dashanji <dashanjic@gmail.com>

designs/helm-chart-autogenerate-plugin.md

@@ -0,0 +1,213 @@
+| Authors       | Creation Date | Status      | Extra |
+|---------------|---------------|-------------|---|
+| @name | date | Implementeble | - |
+
+# Auto-generate Helm Chart Plugin
+===================
+
+The proposal is to add a new alpha command to auto-generate a helm chart for a given kustomize directory created by kubebuilder.
+
+## Example
+
+By running the following command, the plugin will generate a helm chart from the specific kustomize directory and output it to the directory specified by the `--output` flag.
+
+```shell
+kubebuilder alpha generate-helm-chart --from=<path> --output=<path>
+```
+
+## Open Questions [optional]
+
+TBF
+
+## Summary
+
+TBF
+
+## Motivation
+
+Currently, kubebuilder only supports the distribution of the operator by the kustomize. However, many well-known operators contains the distribution of helm charts:
+
+- [mongodb](https://artifacthub.io/packages/helm/mongodb-helm-charts/community-operator
+)
+- [cert-manager](https://cert-manager.io/v1.6-docs/installation/helm/#1-add-the-jetstack-helm-repository)
+- [prometheus](https://bitnami.com/stack/prometheus-operator/helm)
+
+The proposed command will auto-generate a helm chart from a kustomize directory created by kubebuilder with minimizing the manual effort. The generated helm chart will cover the frequently-used configurations.
+
+Context:
+
+- See the discussion [Is there a good solution/tool to generate a new helm chart from the manifests?](https://github.com/kubernetes-sigs/kubebuilder/discussions/3074)
+
+### Goals
+
+- Help developers to generate a helm chart from a kustomize directory.
+- Generate a helm chart without human interactions once the kustomize directory updated.
+- Reserve the ability to customize the helm chart by the developer.
+
+### Non-Goals
+
+- Generate the helm chart from a kustomize directory not created by kubebuilder.
+- Generate the fine-grained configurations.
+
+## Proposal
+
+To reduce the user adaptation, the command
+leverage the existing kustomize default directory and create the similar layout of the helm chart from it. The generated `values.yaml` is as follows:
+
+```yaml
+# global configurations
+nameOverride: ""
+
+fullnameOverride: ""
+
+crd:
+  create: true
+
+## More info: https://kubernetes.io/docs/admin/authorization/rbac/
+rbac:
+  create: true
+  serviceAccountName: ""
+
+
+## Configure the manager
+manager:
+  ## The Security Context of the manager Pod.
+  ## More info: https://kubernetes.io/docs/tasks/configure-pod-container/security-context/#set-the-security-context-for-a-pod
+  podSecurityContext:
+  runAsNonRoot: true
+
+  ## Configure the kubeRbacProxy container.
+  kubeRbacProxy:
+    image:
+     registry: gcr.io
+     repository: "kubebuilder/kube-rbac-proxy"
+     tag: v0.13.0
+     pullPolicy: IfNotPresent
+
+  ## Configure the resources.
+  ## More info: https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/ 
+  resources:
+    limits:
+      cpu: 500m
+      memory: 128Mi
+    requests:
+      cpu: 5m
+      memory: 64Mi
+
+  ## Configure the controller container.
+  controller:
+    image:
+      registry: docker.io
+      repository: ""
+      tag: latest
+      pullPolicy: IfNotPresent
+
+     ## The environment variables of the controller container.
+     ## More info: https://kubernetes.io/docs/tasks/inject-data-application/define-environment-variable-container/
+  	env: []
+
+    ## Configure extra options for liveness probe.
+    ## More info: https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-probes/#configure-probes
+    livenessProbe:
+      enabled: true
+      httpGet:
+        path: /healthz
+        port: 8081
+      initialDelaySeconds: 15
+      periodSeconds: 20
+
+    readinessProbe:
+      enabled: true
+      httpGet:
+        path: /readyz
+        port: 8081
+      initialDelaySeconds: 5
+      periodSeconds: 10
+
+    ## Configure the resources.
+    ## More info: https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/ 
+    resources:
+      limits:
+        cpu: 500m
+        memory: 128Mi
+      requests:
+        cpu: 10m
+        memory: 64Mi
+
+     ## Configure the scheduling rules.
+     ## More info: https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity
+     affinity: {}
+
+     ## More info: https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#nodeselector
+     nodeSelector: {}
+
+     ## More info: https://kubernetes.io/docs/concepts/configuration/taint-and-toleration
+     tolerations: {}
+
+     ## Configure the rbac roles.
+     serviceAccountName: ""
+
+## Configure the webhook
+webhook:
+  enabled: true
+  ## More info: https://kubernetes.io/docs/concepts/services-networking/service/
+  service:
+    type: ClusterIP
+    ports:
+    - port: 443
+      protocol: TCP
+      targetPort: 9443
+
+metrics:
+  enabled: true
+  service:
+    type: ClusterIP
+    ports:
+    - port: 8443
+      protocol: TCP
+
+## Configure the cert-manager
+certmanager:
+  enabled: true
+  installCRDs: true
+  ## Add the owner reference to the certificate.
+  extraArgs:
+  - --enable-certificate-owner-ref=true
+
+prometheus:
+  ## Enable the Prometheus Monitor
+  enabled: false
+
+## The domain name of Kubernetes cluster 
+## More info: https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/
+clusterDomain: cluster.local
+```
+
+### User Stories
+
+- As a developer, I want to be able to generate a helm chart from a kustomize directory so that I can distribute the helm chart to my users. Also, I want the 
+generation to be as simple as possible without the need to write any additional duplicate files.
+
+- As a user, I want the helm chart can cover all potential configurations when I deploy it on the Kubernetes cluster.
+
+### Implementation Details/Notes/Constraints [optional]
+
+TBF
+
+### Risks and Mitigations
+
+TBF
+
+### Proof of Concept [optional]
+
+Refer to the open source tool
+[helmify](https://github.com/arttor/helmify).
+
+
+## Drawbacks
+
+TBF
+
+## Alternatives
+
+TBF