title: MongoDB: aggregation. Don't know how to use it correctly
body: <p>I need help with some project. 
  Maybe somebody could help me.
  I got some data in mongodb.
  Now it looks like:</p>
  
  <pre><code>{
      Order: {
          order_id: id,
          SKU: some_vale,
          date: "10.10.1010",
          time: "12:12",
          product_name: some_name,
          number_of_goodies: some_value
      }
  }
  </code></pre>
  
  <p>And I need to group it to look like:</p>
  
  <pre><code>{
      Order: {
          order_id: id,
          product:
              {
              SKU: some_vale,
              product_name: some_name,
              number_of_goodies: some_value
              }
  
          date: "10.10.1010",
          time: "12:12"
  
      }
  }
  </code></pre>
  
  <p>Now there can be more than one document for one order. They got same order_ID but different products.
  I was trying to use aggregation, but wasn't really successful.
  If someone know how to solve this problem using aggrigation?</p>