title: Mention Users Group via Slack API
body: <p>I would like to mention Users Group via Slack API (Rest), is it possible? I tried via 
      <code>@admins</code>, <code>&lt;@admins&gt;</code>, <code>&lt;@ID&gt;</code>, <code>&lt;!admins&gt;</code></p>
  
  <p>But it still is showed as a standard text, without mention. Any ideas?</p>