code: func newHasKeyHandler(store mock.GlobalStorer) http.HandlerFunc {
  	return func(w http.ResponseWriter, r *http.Request) {
  		addr, key, ok := parseHasKeyPath(r.URL.Path)
  		if !ok {
  			jsonStatusResponse(w, http.StatusNotFound)
  			return
  		}
  		found := store.HasKey(addr, key)
  		if !found {
  			jsonStatusResponse(w, http.StatusNotFound)
  			return
  		}
  		jsonStatusResponse(w, http.StatusOK)
  	}
  }
docs: // newHasKeyHandler returns a new handler that serves
  // requests for HasKey global store method.
  // Possible responses are StatusResponse with
  // status codes 200 or 404 if the chunk is found or not.