title: Angular Service Worker with POST request
body: <p>I use Angular 5.2.7 with Angular Service Worker 5.2.7.</p>
  
  <p>I want to cache webservices calls. So, I've got with this config in my ngsw-config.json, for dataGroups :</p>
  
  <pre><code>"dataGroups": [{
    "name": "tasks-users-api",
    "urls": ["/api", "/rest"],
    "cacheConfig": {
      "strategy": "freshness",
      "maxSize": 20000,
      "maxAge": "1h",
      "timeout": "5s"
    }
  }]
  </code></pre>
  
  <p>I try to cache this two URLs :
  <a href="https://randomuser.me/api/?results=20" rel="noreferrer">https://randomuser.me/api/?results=20</a> ---> It's OK
  <a href="https://test.moodlecloud.com/webservice/rest/server.php" rel="noreferrer">https://test.moodlecloud.com/webservice/rest/server.php</a> ---> It's KO</p>
  
  <p>The first one is cached as expected. It's a simple GET service.
  The second one isn't. It's a POST service with a form data sent as payload.</p>
  
  <p>Any idea of what is wrong with that ?</p>