Add group identification headers to epic emails

Add X-GitLab-Group-Id and X-GitLab-Group_Path headers
on epic emails.

ee/app/mailers/ee/emails/notes.rb

@@ -5,6 +5,7 @@ module EE
     module Notes
       def note_epic_email(recipient_id, note_id, reason = nil)
         setup_note_mail(note_id, recipient_id)
+        add_group_headers
 
         @epic = @note.noteable
         @target_url = group_epic_url(*note_target_url_options)

ee/app/mailers/ee/notify.rb

@@ -26,5 +26,10 @@ module EE
 
       group.full_name
     end
+
+    def add_group_headers
+      headers['X-GitLab-Group-Id'] = group.id
+      headers['X-GitLab-Group-Path'] = group.full_path
+    end
   end
 end

ee/app/mailers/emails/epics.rb

@@ -29,6 +29,8 @@ module Emails
       @group = @epic.group
       @target_url = group_epic_url(@epic.group, @epic)
 
+      add_group_headers
+
       @sent_notification = SentNotification.record(@epic, recipient_id, reply_key)
     end
 

ee/changelogs/unreleased/issue_12786.yml

+---
+title: Add group identification headers to epic emails
+merge_request: 24878
+author:
+type: added

ee/spec/mailers/notify_spec.rb

@@ -298,6 +298,7 @@ describe Notify do
         end
         it_behaves_like 'it should show Gmail Actions View Epic link'
         it_behaves_like 'an unsubscribeable thread'
+        it_behaves_like 'having group identification headers'
 
         it 'has the correct subject and body' do
           prefix = "#{epic.group.name} | "
@@ -329,6 +330,8 @@ describe Notify do
 
         it_behaves_like 'an unsubscribeable thread'
 
+        it_behaves_like 'having group identification headers'
+
         it 'has the characteristics of a threaded reply' do
           host = Gitlab.config.gitlab.host
           route_key = "#{epic.class.model_name.singular_route_key}_#{epic.id}"

ee/spec/support/shared_examples/mailers/notify_shared_examples.rb

@@ -23,4 +23,11 @@ RSpec.shared_examples 'an epic email starting a new thread with reply-by-email e
       is_expected.to have_header 'Reply-To', /<reply@#{Gitlab.config.gitlab.host}>\Z/
     end
   end
+
+  RSpec.shared_examples 'having group identification headers' do
+    it 'has specific group headers' do
+      is_expected.to have_header 'X-GitLab-Group-Id', /#{group.id}/
+      is_expected.to have_header 'X-GitLab-Group-Path', /#{group.full_path}/
+    end
+  end
 end