Imports github.com/jetstack/cert-manager/pkg/api/util github.com/jetstack/cert-manager/pkg/apis/certmanager/v1alpha1 github.com/jetstack/cert-manager/pkg/issuer/acme/dns/rfc2136 k8s.io/api/core/v1 k8s.io/apimachinery/pkg/util/validation/field Standard library imports crypto/x509 fmt net strings