private boolean isHeadBucketRequest(String path) {
    return path.split("/").length <= 3;
  }
Process the request and construct the response according to the
<a href="https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadObject.html">HeadObject spec</a> and
<a href="https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadBucket.html">BucketObject spec</a>

@param restRequest the {@link RestRequest} that contains the request parameters and body.
@param restResponseChannel the {@link RestResponseChannel} where headers should be set.
@param callback the {@link Callback} to invoke when the response is ready (or if there is an exception).
@throws RestServiceException exception when the processing fails
ambry-frontend/src/main/java/com/github/ambry/frontend/s3/S3HeadHandler.java