title: How to alert a custom group in slack using incoming webhook
body: <p>I was trying to alert a custom group using incoming webhook in slack.I can able to alert user using <code>&lt;@user&gt;</code>, but with group any of the following format is not working</p>
  
  <pre><code>&lt;!cgroup&gt;
  &lt;@cgroup&gt;
  </code></pre>
  
  <p>What i am missing here. Thanks in advance.</p>