Gateway.spec.tls.frontend.perPort[].tls.validation.spec.tls.backend.clientCertificateRef

ClientCertificateRef references an object that contains a client certificate and its associated private key. It can reference standard Kubernetes resources, i.e., Secret, or implementation-specific custom resources. A ClientCertificateRef is considered invalid if: * It refers to a resource that cannot be resolved (e.g., the referenced resource does not exist) or is misconfigured (e.g., a Secret does not contain the keys named `tls.crt` and `tls.key`). In this case, the `ResolvedRefs` condition on the Gateway MUST be set to False with the Reason `InvalidClientCertificateRef` and the Message of the Condition MUST indicate why the reference is invalid. * It refers to a resource in another namespace UNLESS there is a ReferenceGrant in the target namespace that allows the certificate to be attached. If a ReferenceGrant does not allow this reference, the `ResolvedRefs` condition on the Gateway MUST be set to False with the Reason `RefNotPermitted`. Implementations MAY choose to perform further validation of the certificate content (e.g., checking expiry or enforcing specific formats). In such cases, an implementation-specific Reason and Message MUST be set. Support: Core - Reference to a Kubernetes TLS Secret (with the type `kubernetes.io/tls`). Support: Implementation-specific - Other resource kinds or Secrets with a different type (e.g., `Opaque`).