title: How to retrieve id of just inserted firestore document (with angularfire2)?
body: <p>I'm inserting a new document into my firestore collection like so:</p>
  
  <pre><code>this.afs.collection&lt;Client&gt;('clients').add(this.form.value).then(docRef =&gt; {
    console.log("Need to output the firestore generated doc id of the document here: ...")
  })
  </code></pre>