title: display nested collection using dataweave
body: <p>I want to display following output (json), the input are from pl/sql cursors, 
  my questions:</p>
  
  <ol>
  <li>how to display this output?</li>
  <li>what kind of input expected in order to have this output?</li>
  <li>how to combine 2 cursor results by using <code>personId</code> key?</li>
  </ol>
  
  <p>Thank you</p>
  
  <p>input:</p>
  
  <pre><code>personCursor: 
  [{personName=a,personId=1}, {personName=b,personId=2}]
  *contactCursor*
  [{personId=1, firstName==x, phone=123}, {personId=1, firstName==y, phone=234}, {personId=2, firstName==z, phone=345},{personId=2, firstName==w, phone=456}]
  **output:**
  [
    {
      "personName": "a",
      "personId": "1",
      "contacts": 
              [
                  {
                      "firstname": "x",
                      "phone": 123
                  },
                  {
                      "firstname": "y",
                      "phone": 234
                  },
              ]
    },
   {
      "personName": "b",
      "personId": "2",
      "contacts": 
              [
                  {
                      "firstname": "z",
                      "phone": 345
                  },
                  {
                      "lastname": "w",
                      "phone": 456
                  },
              ]
    }
  ]
  </code></pre>