This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
- Regular users are not notified of whispers
- Regular users no longer have "stuck" topics in unread
- Additional tracking for staff highest post number
- Remove a bunch of unused columns in topics table
Penar Musaraj
Sam Saffron
Guo Xiang Tan
Robin Ward
Gosha Arinich