title: execute extra observable/promise at the end of the http request
body: <p>I have an interceptor and I need to chain/execute a promise/observable when the request comes back from the server.  How can I do this in rxjs 6?</p>
  
  <pre><code>intercept(): Observable&lt;HttpEvent&lt;any&gt;&gt; {
      return next.handle(request)[DO-SOMETHING]
  }
  </code></pre>