Introduce EXCLUDED_WATCHER_EVENTS to exclude events

for watchers. Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8176#note_20920905

app/models/notification_setting.rb

@@ -37,6 +37,10 @@ class NotificationSetting < ActiveRecord::Base
     :success_pipeline
   ]
 
+  EXCLUDED_WATCHER_EVENTS = [
+    :success_pipeline
+  ]
+
   store :events, accessors: EMAIL_EVENTS, coder: JSON
 
   before_create :set_events

app/services/notification_service.rb

@@ -592,8 +592,7 @@ class NotificationService
 
     recipients = target.participants(current_user)
 
-    # TODO: CLEAN ME UP!
-    unless custom_action == :success_pipeline
+    unless NotificationSetting::EXCLUDED_WATCHER_EVENTS.include?(custom_action)
       recipients = add_project_watchers(recipients, project)
     end