resetSettings (userId, theme) {
    const settings = JSON.parse(JSON.stringify(store.state.userSettingDefaults));

    if (theme) {
      settings.theme = theme;
    }

    return this.saveSettings(settings, userId);
  }
Resets a user's settings
@param {string} userId     The unique identifier for a user
                           (only required if not the current user)
@param {string} theme      Current theme identifier.
                           Avoid resetting the current theme if it exists
@returns {Promise} Promise A promise object that signals the completion
                           or rejection of the request.