Allow global event list containing all events

This way we can globally set group only ee events too.
Use nil to indicate global.

ee/app/models/ee/notification_setting.rb

@@ -4,6 +4,11 @@ module EE
   module NotificationSetting
     extend ActiveSupport::Concern
 
+    EMAIL_EVENTS_MAPPING = {
+      ::Group => [:new_epic]
+    }.freeze
+    FULL_EMAIL_EVENTS = EMAIL_EVENTS_MAPPING.values.flatten.freeze
+
     class_methods do
       extend ::Gitlab::Utils::Override
 
@@ -11,9 +16,14 @@ module EE
       def email_events(source = nil)
         result = super.dup
 
-        case target
-        when Group, :group
-          result << :new_epic
+        if source.nil?
+          # Global setting
+          result.concat(FULL_EMAIL_EVENTS)
+        else
+          source_class = source.is_a?(Class) ? source : source.class
+          EMAIL_EVENTS_MAPPING[source_class]&.tap do |events|
+            result.concat(events)
+          end
         end
 
         result

ee/spec/models/ee/notification_setting_spec.rb

@@ -56,5 +56,31 @@ describe NotificationSetting do
         )
       end
     end
+
+    context 'global' do
+      let(:target) { nil }
+
+      it 'appends EE specific events' do
+        expect(subject).to eq(
+          [
+            :new_note,
+            :new_issue,
+            :reopen_issue,
+            :close_issue,
+            :reassign_issue,
+            :issue_due,
+            :new_merge_request,
+            :push_to_merge_request,
+            :reopen_merge_request,
+            :close_merge_request,
+            :reassign_merge_request,
+            :merge_merge_request,
+            :failed_pipeline,
+            :success_pipeline,
+            :new_epic
+          ]
+        )
+      end
+    end
   end
 end

lib/api/notification_settings.rb

@@ -50,7 +50,9 @@ module API
       end
     end
 
-    %w[group project].each do |source_type|
+    [Group, Project].each do |source_class|
+      source_type = source_class.name.underscore
+
       params do
         requires :id, type: String, desc: "The #{source_type} ID"
       end
@@ -73,7 +75,7 @@ module API
         end
         params do
           optional :level, type: String, desc: "The #{source_type} notification level"
-          NotificationSetting.email_events(source_type.to_sym).each do |event|
+          NotificationSetting.email_events(source_class).each do |event|
             optional event, type: Boolean, desc: 'Enable/disable this notification'
           end
         end