title: Ag-Grid Server Side Row Group Key Creator
body: <p>When using Ag-Grid's server side row model, I am unable to send a custom group key to the server in order to do proper group by queries.</p>
  
  <p>My row data is a simple JSON structure but with one composite object.</p>
  
  <pre><code>row = {
      athlete: '',
      age: '',
      country: {
          name: 'Ireland',
          code: 'IRE'
      },
     ...
  }
  </code></pre>
  
  <p>I am using the server side row model.  To get the grid to display the country name is simple enough as I use the following column definition.</p>
  
  <pre><code>{
   headerName: "Country", 
   colId: "country", 
   valueGetter: "data.country.name", 
   enableRowGroup: true
  }
  </code></pre>
  
  <p>However, when I group by the Country column ag-grid sends the groupKey as 'Ireland' from my example above.  But I need the group key to be the country code, 'IRE'.  I cannot figure out how to generate a groupKey when using the server-side row model.</p>
  
  <p>I have seen the keyCreator method, but this only works for client-side row model.  In addition, I have seen the Tree Data Mode which has a callback for <code>getServerSideGroupKey(dataItem)</code> but then callback only gets used when <code>gridOptions.treeData = true</code> and when the treeData option is set to true, a "Group" column is always displayed regardless if a grouping is happening or not.  I tested this out by setting <code>isServerSideGroup: function(dataItem) {return false;}</code></p>
  
  <p>Any help would be appreciated.  </p>