Instrument Rinku usage

CHANGELOG

@@ -28,6 +28,7 @@ v 8.10.0 (unreleased)
   - Better caching of git calls on ProjectsController#show.
   - Add API endpoint for a group issues !4520 (mahcsig)
   - Add Bugzilla integration !4930 (iamtjg)
+  - Instrument Rinku usage
   - Metrics for Rouge::Plugins::Redcarpet and Rouge::Formatters::HTMLGitlab
   - Allow [ci skip] to be in any case and allow [skip ci]. !4785 (simon_w)
   - Add basic system information like memory and disk usage to the admin panel

config/initializers/metrics.rb

@@ -135,6 +135,8 @@ if Gitlab::Metrics.enabled?
     config.instrument_instance_methods(Rouge::Plugins::Redcarpet)
     config.instrument_instance_methods(Rouge::Formatters::HTMLGitlab)
+
+    config.instrument_methods(Rinku)
   end
   GC::Profiler.enable