title: Observable <boolean> dont return java value
body: <p>iam trying to make a request for backend for a boolean value with observable but i cant get there, dont know what is the best option .map .subscribe</p>
  
  <pre><code>return this.http.put({url}, credentials, this.requestOptions)
      .catch((error: any) =&gt; Observable.throw(error.message)).map((res...
  </code></pre>
  
  <p>the call is to a api that returns boolean</p>
  
  <pre><code>    @PutMapping("/url")
  public Boolean api(@RequestBody Credentials credentials)
  </code></pre>
  
  <p>how can i get that boolean value back in typescript? </p>