static boolean hasAChild(ConfigKey<?> key, Set<ConfigKey<?>> keys) {
            if ("".equals(key.getConfigId())) return false;
            for (ConfigKey<?> k : keys) {
                if (!k.getName().equals(key.getName())) continue;
                if ("".equals(k.getConfigId())) continue;
                if (k.getConfigId().equals(key.getConfigId())) continue;
                if (k.getConfigId().startsWith(key.getConfigId())) return true;
            }
            return false;
        }
The listing URL for this config in this service

@param key config key
@param rec recursive
@return url
configserver/src/main/java/com/yahoo/vespa/config/server/http/v2/HttpListConfigsHandler.java