title: Extending a child object with Knockout Mapping
body: <p>Consider this JSON object:</p>
  
  <pre><code>{
      "BusinessModels":[
          { 
              "Id":1,
              "Name":"Business to Business",
              "Businesses":[],
              "ReportTypes":[
                  {...},
                  {...},
                  {
                      "Id":6,
                      "Name":"Risk",
                      "BusinessModelId":1,
                      "Reports":[
                          {
                              "Id": 4,
                              "Name": "Test",
                              "Value": ko.observable() // NEED TO ADD THIS PROPERTY USING MAPPING
                          },
                          {...}
                      ]
                  }
              ],
          }
      ]
  }
  </code></pre>
  
  <p>I'm trying to add the value using the following code, but it doesn't seem to work.</p>
  
  <pre><code>var mapping = {
      'BusinessModels': {
          create: function(options) {
              return new function() {
                  var self = options.data;
                  self.SelectedBusiness = ko.observable();
                  self.Businesses.unshift({ Id: 0, Name: 'All Clients' });
                  ko.mapping.fromJS(self, {}, this);
              };
          }
      },
      'Reports': {
          create: function (options) {
              return new function () {
                  var self = options.data;
                  self.Value = ko.observable();
                  ko.mapping.fromJS(options.data, {}, this);
              };
          }
       }
  };
  
  var model = ko.mapping.fromJSON(raw, mapping);
  ko.applyBindings(model);
  </code></pre>
  
  <p>I need to give a child object "Reports" a <code>ko.observable</code> object named <code>Value</code>. How do I go about doing this in ko.mapping?</p>