private void writeUserDefs(ApplicationPackage applicationPackage) {
            Map<ConfigDefinitionKey, UnparsedConfigDefinition> configDefs = applicationPackage.getAllExistingConfigDefs();
            for (Map.Entry<ConfigDefinitionKey, UnparsedConfigDefinition> entry : configDefs.entrySet()) {
                ConfigDefinitionKey key = entry.getKey();
                String contents = entry.getValue().getUnparsedContent();
                writeConfigDefinition(key.getName(), key.getNamespace(), getZooKeeperAppPath(USER_DEFCONFIGS_ZK_SUBPATH), contents);
                writeConfigDefinition(key.getName(), key.getNamespace(), getZooKeeperAppPath(DEFCONFIGS_ZK_SUBPATH), contents);
            }
            if ( ! configDefs.isEmpty())
                logger.log(Level.FINE, () -> configDefs.size() + " user config definitions");
        }
Feeds all user-defined .def file from the application package into ZooKeeper (both into
/defconfigs and /userdefconfigs
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ZooKeeperDeployer.java