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
Previously it would unhide their post but leave them silenced.
This fix also cleans up some of the helper classes to make it easier
to pass extra data to the silencing code (for example, a link to the
post that caused the user to be silenced.)
This patch also refactors the auto_silence specs to avoid using
stubs.
