title: Find all docs where field doesn't exists, plus if field exists apply condition
body: <p>Is there a way to make a query that:</p>
  
  <ul>
  <li>if certain field exists, it will apply condition on the field and if it pass, it will add return document and add it to the results. </li>
  <li><strong>and</strong> if such field doesn't exist, it will also add document to the results?</li>
  </ul>
  
  <p>In the end we will receive all documents where certain field have matched condition <strong>AND</strong> all document where such field doesn't exist at all.</p>