title: How to override parent schema field with discriminators using mongoosejs
body: <p>I have a parent schema Post:</p>
  
  <pre><code>{
      title: {
          type: String,
          required: true
      },
      authors: {
          type: [String],
          required: true
      }
   }
  </code></pre>
  
  <p>I want to make a child schema inheriting on this using the discriminator() mongoose function, but I want to add extra validation on the authors field to make sure the array it not empty. </p>
  
  <p>How can I do this?</p>
  
  <p>Also, could anyone point me to good documentation on mongoose discriminators. The official documentation hasn't been helpful in my search.</p>