title: Add object inside nested array in Mongoose
body: <p>I am working on a web app (using Mongoose).</p>
  <p>This is my <strong>Users JSON</strong>:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>[
    {
      _id:'2819vnablj3490fa',
      name:'Bob',
      subscriptions:[
        {
          _id:'s3989408121',
          plan:'Premium',
          services:[
            {
              _id:'2237fdas2323',
              service_name:'Insurance',
            },
             {
              _id:'37280172918',
              service_name:'Consulting',
            },
              {
              _id:'27847378172',
              service_name:'Consulting',
            }
          ]
        }
      ]
    }
  ]</code></pre>
  </div>
  </div>
  </p>
  <p>In my example I would like to:</p>
  <ol>
  <li>Get user with id= <strong>2819vnablj3490fa</strong> (Bob)</li>
  <li>Get subscription with id = <strong>s3989408121</strong></li>
  <li>Add a new service (<em>{_id:'1920910212',service_name:'Scouting'}</em>) to services</li>
  </ol>
  <p>I tried to do the following:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>var new_service = {id:'1920910212',service_name:'Scouting'}
  
    Label.findOneAndUpdate(
        { _id: "2819vnablj3490fa","subscriptions._id":"s3989408121"},
        { $addToSet: {services:new_service} }
      );</code></pre>
  </div>
  </div>
  </p>
  <p>Actually, this is one of the many solutions that I have adopted but I still can't get out of it.</p>
  <p>Could u help me ?</p>