title: Mongoose: Find all Models using array of objects
body: <p>I have this Model:</p>
  <pre><code>const cart = new mongoose.Schema(
    {
      products: [{
          productId: {
              type: mongoose.Schema.Types.ObjectId,
              ref: &quot;Product&quot;,
          },
          quantity: {
              type: Number,
              required: true,
              default: 1
          },
          title: String,
          price: Number
      }],
    },
    { timestamps: true });
  </code></pre>
  <p>How I find all my products (from Model Product) using it.</p>
  <pre><code>cart = Cart.find(id);
  
  // inside cart.products
  [{productId: 'asvhbajAS13', quantity: 8 },{productId: 'asvhbajAS13', quantity: 2 }]
  </code></pre>
  <p>I want to modify all products after that, is this approach right?</p>
  <p>What I've tried:</p>
  <pre><code>Product.find({
                  '_id': { $in: { cart.products } }
               }, function(err, product) {
                
                  })
          });
  </code></pre>