code: func (ub *URLBuilder) BuildBlobURL(ref reference.Canonical) (string, error) {
  	route := ub.cloneRoute(RouteNameBlob)
  
  	layerURL, err := route.URL("name", ref.Name(), "digest", ref.Digest().String())
  	if err != nil {
  		return "", err
  	}
  
  	return layerURL.String(), nil
  }
docs: // BuildBlobURL constructs the url for the blob identified by name and dgst.