title: Is it possible to filter on Open Extensions?
body: <p>I'm looking to decide on Open Extensions vs. Schema Extensions.</p>
  
  <p>Schema Extensions I know I can filter on, but I end up with an ugly schema name since I don't have any valid tld registered. This is not a blocker, just a small irritation :)</p>
  
  <p>I'm adding custom metadata to a Group, and want to limit a query to all Groups having a specific metadata value. Is this doable using Open Extensions?</p>
  
  <p>All OData variations I have tried using <code>/groups?$filter=</code> seem to give errors.</p>