title: Use pipe on bindLabel at <ng-select>
body: <pre><code>&lt;ng-select 
      [items]="prozessItem$ | async" 
      [multiple]="true" 
      bindLabel="itemName | umlautsPipe" 
      bindValue="nrItems"
  &gt;&lt;/ng-select&gt;
  </code></pre>
  
  <p>I want to pipe the itemName from <code>"üäößTEST"</code> to <code>"ueaeoessTest"</code>. The async pipe works just fine and without the pipe I get <code>"üäößTEST"</code>. Ng-select only accepts a string value in the attribute. I may be misunderstanding it but I believe that when I use <code>bindLabel="itemName | umlautsPipe"</code>, ng-select is attempting to reference <code>item[itemName | umlautsPipe]</code> which does not exist.</p>
  
  <p>So how can I transform the name of the item?</p>