Instrument all Grape API helpers

CHANGELOG

@@ -57,6 +57,7 @@ v 8.8.0 (unreleased)
   - Redesign navigation for profile and group pages
   - Add counter metrics for rails cache
   - Import pull requests from GitHub where the source or target branches were removed
+  - All Grape API helpers are now instrumented
 
 v 8.7.6
   - Fix links on wiki pages for relative url setups. !4131 (Artem Sidorenko)

config/initializers/metrics.rb

@@ -118,6 +118,8 @@ if Gitlab::Metrics.enabled?
     # Instrument the classes used for checking if somebody has push access.
     config.instrument_instance_methods(Gitlab::GitAccess)
     config.instrument_instance_methods(Gitlab::GitAccessWiki)
+
+    config.instrument_instance_methods(API::Helpers)
   end
 
   GC::Profiler.enable