code: func (buh *blobUploadHandler) writeBlobCreatedHeaders(w http.ResponseWriter, desc distribution.Descriptor) error {
  	ref, err := reference.WithDigest(buh.Repository.Named(), desc.Digest)
  	if err != nil {
  		return err
  	}
  	blobURL, err := buh.urlBuilder.BuildBlobURL(ref)
  	if err != nil {
  		return err
  	}
  
  	w.Header().Set("Location", blobURL)
  	w.Header().Set("Content-Length", "0")
  	w.Header().Set("Docker-Content-Digest", desc.Digest.String())
  	w.WriteHeader(http.StatusCreated)
  	return nil
  }
docs: // writeBlobCreatedHeaders writes the standard headers describing a newly
  // created blob. A 201 Created is written as well as the canonical URL and
  // blob digest.