* feat: Allow reviewer to accept a review they're previously rejected
* feat: Add a reviewer who has previously rejected a review to the list of suggested reviewers.
This largely un-does d105f8b, at the request of at least one team secretary.
* fix: Went a little overboard on the previous commit
one_assignment still has to exclude reviewers who rejected the assignment,
or they could end up being the suggested reviewer.
* fix: Actually do the assignment
* fix: If there's an existing assignment, don't create a new one
* style: Restructure conditional for clarity
* test: Add test cases for accepting or assigning a review assignment after rejecting it
c718fedb6c