If two review requests are marked as depending on each other, serializing

things to the API would fail due to the circular reference. The issue here is

that the draft model on the frontend was requesting that the depends on field

be expanded.
The only reason it was needing to be expanded was because it wanted to get the

"url" field. Since we already had custom serializers for the links in the

review request model, I've extended these a bit to add the URL field (and

copied them to the draft resource), so we don't need to fetch the fully

expanded dependency object.

Set two review requests to depend on each other. Verified that I could now make

changes to the drafts without getting 500 errors.