@Override
    public String toString() {
        return toString(this, vfs(), clock(), entryCacheSpec(), maxCacheEntrySizeBytes(),
                        serveCompressedFiles(), autoIndex(), headers(), mediaTypeResolver(),
                        fallbackFileExtensions());
    }
Returns the file extensions that are appended to the file name when the file is not found.
core/src/main/java/com/linecorp/armeria/server/file/FileServiceConfig.java