title: Mongoose default sorting order
body: <p>Is there a way to specify sorting order on the schema/model level in Mongoose?</p>
  
  <p>I have model <code>Posts</code>, and I always fetch posts ordered by <code>'createdAt'</code> field. Thus on each query I have to write <code>.sort('-createdAt')</code>. Can I make this order default for this model?</p>