helm-external-secrets/docs/snippets/certsans-template-v2-external-secret.yaml

apiVersion: external-secrets.io/v1
kind: ExternalSecret
metadata:
  name: cert-sans-example
spec:
  # ...
  target:
    template:
      engineVersion: v2
      data:
        # Store all SANs as a comma-separated string
        sans: '{{ .certificate | filterPEM "CERTIFICATE" | filterCertChain "leaf" | certSANs | join "," }}'
        # Store the first SAN (e.g. primary domain)
        primary-domain: '{{ index (.certificate | filterPEM "CERTIFICATE" | filterCertChain "leaf" | certSANs) 0 }}'
        # Store SANs as a JSON array
        sans-json: '{{ .certificate | filterPEM "CERTIFICATE" | filterCertChain "leaf" | certSANs | toJson }}'