Don't email issue email participants confidential comments

Recently introduced ocnfidential comments are being emailed
to issue email participants (when they should not). This
adds a check of comment confidentiality before deciding whether
an email should be sent to the issue email partcipants.

Changelog: fixed

app/services/notification_service.rb

@@ -384,6 +384,7 @@ class NotificationService
 
   def send_service_desk_notification(note)
     return unless note.noteable_type == 'Issue'
+    return if note.confidential
 
     issue = note.noteable
     recipients = issue.email_participants_emails

changelogs/unreleased/329366-dont-email-issue-email-participants-confidential-comments.yml

+---
+title: Don't email issue email participants confidential comments
+merge_request: 60594
+author: Lee Tickett @leetickett
+type: fixed

spec/services/notification_service_spec.rb

@@ -412,7 +412,7 @@ RSpec.describe NotificationService, :mailer do
           it_should_not_email!
         end
 
-        context 'do exist' do
+        context 'do exist and note not confidential' do
           let!(:issue_email_participant) { issue.issue_email_participants.create!(email: 'service.desk@example.com') }
 
           before do
@@ -422,6 +422,18 @@ RSpec.describe NotificationService, :mailer do
 
           it_should_email!
         end
+
+        context 'do exist and note is confidential' do
+          let(:note) { create(:note, noteable: issue, project: project, confidential: true) }
+          let!(:issue_email_participant) { issue.issue_email_participants.create!(email: 'service.desk@example.com') }
+
+          before do
+            issue.update!(external_author: 'service.desk@example.com')
+            project.update!(service_desk_enabled: true)
+          end
+
+          it_should_not_email!
+        end
       end
 
       describe '#new_note' do