S secret for client certificates with an additional
<code>ca.crt</code> key for CA certificates and <code>ca.crl</code> key for
certificate revocation list(CRL) is also supported.
Only one of client certificates and CA certificate
or credentialName can be specified.</p>
<p><strong>NOTE:</strong> This field is applicable at sidecars only if
<code>DestinationRule</code> has a <code>workloadSelector</code> specified.
Otherwise the field will be applicable only at gateways, and
sidecars will continue to use the