title: Bind tooltips to each circleMarker contained in the FeatureGroup in Leaflet
body: <p>I'm implementing a service that shows the last position of users in a Leaflet map. With CircleMarkers I would like to represent the various positions received and set a tooltips with the user's name. I add all the various positions to a FeatrueGroup object. </p>
  
  <p>The positions of the users are refreshate every 10s.</p>
  
  <pre><code>...
  this.featureGroup = L.featureGroup();
  for (let user of this.users) {
    let circleMarker = L.circleMarker(user.latest_gps_point).addTo(this.featureGroup);
  }
  
  this.featureGroup.addTo(this.leafletMap);
  this.realTimePositions();
  </code></pre>
  
  <p>How do I bind a tooltip to each circleMarker in FeatureGroup?</p>