@UnstableApi
    public FutureTransformingRequestPreparation<ResponseEntity<Path>> asFile(File file) {
        requireNonNull(file, "file");
        return asFile(file.toPath());
    }
Writes the content of the {@link HttpResponse} to the {@link File}.
For example:
<pre>{@code
WebClient client = WebClient.of("https://api.example.com");
CompletableFuture<ResponseEntity<File>> response =
    client.prepare()
          .get("/v1/items/1")
          .asFile(new File("..."))
          .execute();
}</pre>
core/src/main/java/com/linecorp/armeria/client/WebClientRequestPreparation.java