private void registerEntries(ConfigPayloadBuilder builder,
                                 Map<Path, FileReference> registeredFiles,
                                 Map<String, ?> entries,
                                 boolean isModelType) {
        for (Map.Entry<String, ?> entry : entries.entrySet()) {
            String name = entry.getKey();
            ConfigPayloadBuilder fileEntry = builder.getObject(name);
            if (isEmptyOptionalPath(entry, fileEntry)) continue;
            if (fileEntry.getValue() == null || fileEntry.getValue().equals("."))
                throw new IllegalArgumentException("Invalid config value '" + fileEntry.getValue() + "' for field '" + name);
            registerFileEntry(fileEntry, registeredFiles, isModelType);
        }
    }
Registers user configured files for a producer for file distribution.
config-model/src/main/java/com/yahoo/vespa/model/filedistribution/UserConfiguredFiles.java