If you create a new review request, fill out the description, testing done, etc. information, and then discard it without publishing, the information that you filled out will no longer be in the review request. With this fix, the draft information is copied over on private unpublished review requests.

All existing unit tests were run and passed.
Added two unit tests to check behaviour of discarding a private unpublished review request (this one should have the change description updated based on the request draft) and discarding a public unpublished review request (this should not have the change description updated and behaves like it used to).
Manually tested combinations of: filling out the information (description, testing done, file attachments) of a new review request, discarding it, reopening it, modifying/not modifying fields, and discarding it again.