title: Overriding estimatedItemSize for UICollectionViewCell
body: <p>I have a UICollectionView with a flow layout and an estimatedItemSize: <code>flowLayout.estimatedItemSize = CGSize(width: view.frame.width, height: 120)</code></p>
  
  <p>How can I make sure that my cell is autosizing itself so if it's larger than 120, it displays correctly? Is it just a matter of making sure that there's a full chain of constrained subviews connected to the top and bottom or a function I can call?</p>