title: How to add attributes to Jinja2's rendered tag
body: <p><code>{{ form.banner_name }}</code> will render in my template as: </p>
  
  <p><code>&lt;input id="banner_name" name="banner_name" type="text" value=""&gt;</code></p>
  
  <p>How do I add class <code>.form-control</code> to this rendered tag from my template?</p>