Move N_ calls into separate files

These are dynamic translations, so has to be marked explicitly using `N_`,
but they are not used in runtime, so can exist in separate file.
https://github.com/grosser/gettext_i18n_rails#unfound-translations-with-rake-gettextfind

.rubocop.yml

@@ -48,6 +48,8 @@ Naming/FileName:
     - 'qa/bin/*'
     - 'config/**/*'
     - 'lib/generators/**/*'
+    - 'locale/unfound_translations.rb'
+    - 'ee/locale/unfound_translations.rb'
     - 'ee/lib/generators/**/*'
   IgnoreExecutableScripts: true
   AllowedAcronyms:

app/helpers/notifications_helper.rb

@@ -88,16 +88,6 @@ module NotificationsHelper
     when :success_pipeline
       s_('NotificationEvent|Successful pipeline')
     else
-      N_('NotificationEvent|New note')
-      N_('NotificationEvent|New issue')
-      N_('NotificationEvent|Reopen issue')
-      N_('NotificationEvent|Close issue')
-      N_('NotificationEvent|Reassign issue')
-      N_('NotificationEvent|New merge request')
-      N_('NotificationEvent|Close merge request')
-      N_('NotificationEvent|Reassign merge request')
-      N_('NotificationEvent|Merge merge request')
-      N_('NotificationEvent|Failed pipeline')
       s_(event.to_s.humanize)
     end
   end

app/models/notification_setting.rb

@@ -45,6 +45,7 @@ class NotificationSetting < ActiveRecord::Base
     :success_pipeline
   ].freeze
 
+  # Update unfound_translations.rb when events are changed
   def self.email_events(source = nil)
     EMAIL_EVENTS
   end

locale/unfound_translations.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+# Dynamic translations which needs to be marked by `N_` so they can be found by `rake gettext:find`, see:
+# https://github.com/grosser/gettext_i18n_rails#unfound-translations-with-rake-gettextfind
+
+# NotificationSetting.email_events
+N_('NotificationEvent|New note')
+N_('NotificationEvent|New issue')
+N_('NotificationEvent|Reopen issue')
+N_('NotificationEvent|Close issue')
+N_('NotificationEvent|Reassign issue')
+N_('NotificationEvent|New merge request')
+N_('NotificationEvent|Close merge request')
+N_('NotificationEvent|Reassign merge request')
+N_('NotificationEvent|Merge merge request')
+N_('NotificationEvent|Failed pipeline')