Enables frozen string for the following: * app/controllers/*.rb * app/controllers/admin/**/*.rb * app/controllers/boards/**/*.rb * app/controllers/ci/**/*.rb * app/controllers/concerns/**/*.rb Partially addresses #47424.
This whitelists all existing offenses for the various CodeReuse cops, of which most are triggered by the CodeReuse/ActiveRecord cop.
With text/calendar as Content-Type, the browser always downloads the content as a file (even ignoring the Content-Disposition header). We want to display the content inline when accessed from GitLab, similarly to the RSS feed.