Review resources are currently child resources of review requests. This limits
the type of queries we can do for reviews, for example we can't query for all
reviews created by a given user.
This change adds a top-level API endpoint for reviews. We register a root list
resource for reviews and support GET requests with the following query
parameters:
- user=<username>
- repository=<repoName>
- last-updated-from
and last-updated-to
- review-group=<groupName>
Based on work by Taylor Christie at /r/12028.