title: Sort with ignore case in an aggregation
body: <p>I am trying to sort my result with the case insensitive option. So here is my code:</p>
  
  <pre><code>List&lt;AggregationOperation&gt; operations = new ArrayList&lt;&gt;();   
  Sort.Order sort = ....ignoreCase();
  operations.add(new SortOperation(new Sort(sort)));
  </code></pre>
  
  <p>But when I execute my query using an aggregation, it doesn't work:</p>
  
  <pre><code>mongoOperations.aggregate(Aggregation.newAggregation(operations).withOptions(aggregationOptions)
  </code></pre>
  
  <p>I displayed the query in the debug console and the ignoreCase totally disappeared in the aggregation:</p>
  
  <pre><code>db.getCollection('persons').aggregate([   
      {  
        "$sort":{  
          "buyer.organization.name":-1
        }
      }
  ])
  </code></pre>
  
  <p>How can I put the ignore case option in my aggregation?<br><br>
  Thanks for your help!</p>