This PR fixes an issue where the number of flags belonging to a project
was wrong in the new getProjectsForAdminUi.
The cause was that we now join with the events table to get the most
"lastUpdatedAt" data. This meant that we got multiple rows for each
flag, so we counted the same flag multiple times. The fix was to use a
"distinct".
Additionally, I used this as an excuse to write some more tests that I'd
been thinking about. And in doing so also uncovered another bug that
would only ever surface in verrry rare conditions: if a flag had been
created in project A, but moved to project B AND the
feature-project-change event hadn't fired correctly, project B's last
updated could show data from that feature in project A.
I've also taken the liberty of doing a little bit of cleanup.
