title: Use 'virtual' in an array of objects (Mongoose)
body: <p>I have two schemas as the following:</p>
  <pre><code>const castListSchema = new Schema({
    id: String,
    roleInVideo: String
  });
  
  const videoSchema = new Schame({
    castList: { type: [castListSchema], default: [] }
  });
  </code></pre>
  <p>I want to get data by the following structure:</p>
  <pre><code>castList: [
    {
      details: { ... },
      roleInVideo: 'director'
  
    },
    ...
  ]
  </code></pre>
  <p>I want to use <code>virtual</code> not <code>aggregate</code> and etc...</p>
  <p>Is it possible? How?</p>