code: function updateCard(card, options) {
    return webdav.updateObject(card.url, card.addressData, card.etag, options);
  }
docs: @param {dav.VCard} card updated vcard object.
  @return {Promise} promise will resolve when the card has been updated.
  
  Options:
  
  (dav.Sandbox) sandbox - optional request sandbox.
  (dav.Transport) xhr - request sender.