Re-enable post view counts, post search counts, and missed search
counts. These were disabled in 89adf88d5 because of a bug caused by the
upgrade to rack-2.0.8 in a58dd83ad.
The bug was that rack-2.0.8 changed `session.id` to return a value of a
new wrapper type that doesn't respond to `to_s`. Previously it just
returned a string. Now we have to call `session[:session_id]` or
`session.id.public_id` to get a plain string. This was an undocumented
breaking change in rack-2.0.8 to fix CVE-2019-16782.
231e4872ed