title: Mongoose find, then populate, then rename subdocument
body: <p>How do I populate an index inside of a list and afterwards rename one of the indexes? Say I have the following schema's</p>
  <pre><code>const supplierSchema = new mongoose.Schema({
      name: String,
      address: String,
      ... (19 other fields)
      supplier_id: mongoose.Schema.Types.ObjectId,
  });
  
  const itemsSchema = new mongoose.Schema({
      name: String,
      supplier_id: mongoose.Schema.Types.ObjectId,
      item_id: mongoose.Schema.Types.ObjectId,
  });                                                                                                                                                                                                     
                                                                                                                                                                                                                                                                                                                                                                                   
  const receiptSchema = new mongoose.Schema({
      items: [itemSchema]
      receipt_id: mongoose.Schema.Types.ObjectId,
  });
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
  const Receipt = mongoose.model('Photo', photoSchema);
  </code></pre>
  <p>My Receipt is populated such that</p>
  <pre><code>Receipt.findById(&lt;insertID&gt;) currently gives:
  {
      receipt_id: ObjectId(&quot;...&quot;),
      items: [
        {
          name: &quot;...&quot;,
          supplier_id: ObjectId(&quot;...&quot;),
          item_id: ObjectId(&quot;...&quot;)
        },
        {
          name: &quot;...&quot;,
          supplier_id: ObjectId(&quot;...&quot;),
          item_id: ObjectId(&quot;...&quot;)
        }
      ],
    receipt_id: ObjectId(&quot;...&quot;),
  }
  </code></pre>
  <p>I would like for it to populate the <code>supplier_id</code> with <code>name</code> and <code>address</code>. And then rename the <code>supplier_id</code> to <code>supplier</code>.</p>