code: func (api UsersAPI) GetUserPhonenumberByLabel(w http.ResponseWriter, r *http.Request) {
  	username := mux.Vars(r)["username"]
  	label := mux.Vars(r)["label"]
  	userMgr := user.NewManager(r)
  
  	userobj, err := userMgr.GetByName(username)
  	if err != nil {
  		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
  		return
  	}
  
  	phonenumber, err := userobj.GetPhonenumberByLabel(label)
  	if err != nil {
  		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
  		return
  	}
  
  	w.Header().Set("Content-Type", "application/json")
  	json.NewEncoder(w).Encode(phonenumber)
  }
docs: // GetUserPhonenumberByLabel is the handler for GET /users/{username}/phonenumbers/{label}