app.py

<apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: dk-cfg
spec:
  refreshInterval: 30
  secretStoreRef:
    name: example
    kind: SecretStore
  target:
    template:
      type: kubernetes.io/dockerconfigjson
      data:
        .dockerconfigjson: '{"auths":{"{{ .registryName | lower }}.{{ .registryHost }}":{"username":"{{ .registryName }}","password":"{{ .password }}","auth":"{{ printf "%s:%s" .registryName .password | b64enc }}"}}}'
  data:
  - secretKey: registryName
    remoteRef:
      key: secret/docker-registry-name # "myRegistry"
  - secretKey: registryHost
    remoteRef:
      key: secret/docker-registry-host # "docker.io"
  - secretKey: password
    remoteRef:
      key: secret/docker-registry-password>