private static boolean hasS3UrlInConfig(ApplicationContainerCluster cluster) {
        return cluster.userConfiguredUrls().all().stream()
                .anyMatch(url -> url.startsWith("s3://"));
    }
Validates that config using s3:// urls is used in public system and with nodes that are exclusive.

@author hmusum
config-model/src/main/java/com/yahoo/vespa/model/application/validation/UrlConfigValidator.java