What is the best practice for injecting a secret from Google Secret Manager into a Kubernetes deployment? I have stored the admin password for my Grafana instance into Google Secret Manager. The Grafana instance was deployed using a helm chart on Google Kubernetes Engine. I did try using kube-secrets-init, which is a Kubernetes mutating admission webhook, that mutates any K8s Pod that is referencing a secret Google Secret Manager. I followed the instructions, but when I deploy my Grafana instance, I get the following error:

Internal error occurred: failed calling webhook "secrets-init.doit-intl.com": expected webhook response of admission.k8s.io/v1, Kind=AdmissionReview, got /, Kind=

This is the file used to deploy the mutating webhook:

apiVersion: admissionregistration.k8s.io/v1
kind: MutatingWebhookConfiguration
metadata:
  name: mutating-secrets-init-webhook-cfg
  labels:
    app: secrets-init-webhook
webhooks:
  - name: secrets-init.doit-intl.com
    clientConfig:
      service:
        name: secrets-init-webhook-svc
        namespace: default
        path: "/pods"
      caBundle: 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
    admissionReviewVersions: ["v1"]
    sideEffects: None
    rules:
      - operations: [ "CREATE" ]
        apiGroups: ["*"]
        apiVersions: ["*"]
        resources: ["pods"]