default CompletableFuture<Void> postProcessRequest(RestRequest restRequest) {
    CompletableFuture<Void> future = new CompletableFuture<>();
    postProcessRequest(restRequest, CallbackUtils.fromCompletableFuture(future));
    return future;
  }
Similar to {@link #postProcessRequest(RestRequest, Callback)} but returns a {@link CompletableFuture} instead of requiring
a callback.
@param restRequest {@link RestRequest} upon which validations has to be performed
@return a {@link CompletableFuture} that is completed when the post-processing is done.
ambry-api/src/main/java/com/github/ambry/frontend/SecurityService.java