<div class="checkbox">
  <label ng-click="model[options.key] = !model[options.key]">
    <i class="fa" ng-class="model[options.key] ? 'fa-check-square-o' : 'fa-square-o'"></i>
    {{to.label}}
    {{to.required ? '*' : ''}}
  </label>
</div>
