private static String errorMessage(String clusterName, String clientId, String message) {
        return "Client **%s** defined for cluster **%s** contains an invalid certificate: %s"
                .formatted(clientId, clusterName, message);
    }
Validates that trusted data plane certificates are valid

@author bjorncs
config-model/src/main/java/com/yahoo/vespa/model/application/validation/CloudClientsValidator.java