static Set<ConfigKey<?>> keysThatHaveAChildWithSameName(Collection<ConfigKey<?>> keys, Set<ConfigKey<?>> allConfigs) {
            Set<ConfigKey<?>> ret = new LinkedHashSet<>();
            for (ConfigKey<?> k : keys) {
                if (ListConfigsResponse.hasAChild(k, allConfigs)) ret.add(k);
            }
            return ret;
        }
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/HttpListConfigsHandler.java