Add missing email suffix for Emails On Push and Admin emails

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/213383

**Problem**

A custom email suffix is missing for `Emails on Push` and `Admin
notifications`.

**Solution**

Use `#subject` method to wrap subject text. It automatically applies
email suffix if it's missing.

Changelog: fixed

app/mailers/emails/admin_notification.rb

@@ -2,18 +2,18 @@
 
 module Emails
   module AdminNotification
-    def send_admin_notification(user_id, subject, body)
+    def send_admin_notification(user_id, subj, body)
       user = User.find(user_id)
       email = user.notification_email_or_default
       @unsubscribe_url = unsubscribe_url(email: Base64.urlsafe_encode64(email))
       @body = body
-      mail_with_locale to: email, subject: subject
+      mail_with_locale to: email, subject: subject(subj)
     end
 
     def send_unsubscribed_notification(user_id)
       user = User.find(user_id)
       email = user.notification_email_or_default
-      mail_with_locale to: email, subject: "Unsubscribed from GitLab administrator notifications"
+      mail_with_locale to: email, subject: subject("Unsubscribed from GitLab administrator notifications")
     end
   end
 end

app/mailers/emails/projects.rb

@@ -82,7 +82,7 @@ def repository_push_email(project_id, opts = {})
       mail_with_locale(
         from: sender(@message.author_id, send_from_user_email: @message.send_from_committer_email?),
         reply_to: @message.reply_to,
-        subject: @message.subject
+        subject: subject_with_suffix([@message.subject])
       )
     end
 

spec/mailers/emails/admin_notification_spec.rb

@@ -11,4 +11,26 @@
       expect(Notify).to be_respond_to(email_method)
     end
   end
+
+  describe '#send_admin_notification' do
+    subject { Notify.send_admin_notification(recipient.id, 'Subject', 'Body') }
+
+    it 'sends an email' do
+      expect(subject).to have_subject 'Subject'
+      expect(subject).to have_body_text 'Body'
+    end
+
+    it_behaves_like 'an email with suffix'
+  end
+
+  describe '#send_unsubscribed_notification' do
+    subject { Notify.send_unsubscribed_notification(recipient.id) }
+
+    it 'sends an email' do
+      expect(subject).to have_subject 'Unsubscribed from GitLab administrator notifications'
+      expect(subject).to have_body_text 'You have been unsubscribed'
+    end
+
+    it_behaves_like 'an email with suffix'
+  end
 end

spec/mailers/emails/projects_spec.rb

@@ -180,6 +180,24 @@
     end
   end
 
+  describe '#repository_push_email' do
+    let(:recipient) { user }
+
+    subject { Notify.repository_push_email(project.id, { author_id: user.id, ref: 'main', action: :create }) }
+
+    it_behaves_like 'it should not have Gmail Actions links'
+    it_behaves_like 'a user cannot unsubscribe through footer link'
+    it_behaves_like 'appearance header and footer enabled'
+    it_behaves_like 'appearance header and footer not enabled'
+    it_behaves_like 'an email with suffix'
+
+    it 'has the correct subject and body' do
+      is_expected.to have_subject("[Git][#{project.full_path}] Pushed new branch main")
+      is_expected.to have_body_text(project.full_path)
+      is_expected.to have_body_text("#{user.name} pushed new branch main at")
+    end
+  end
+
   describe '.inactive_project_deletion_warning_email' do
     let(:recipient) { user }
     let(:deletion_date) { "2022-01-10" }

spec/support/shared_examples/mailers/notify_shared_examples.rb

@@ -36,6 +36,16 @@
   end
 end
 
+RSpec.shared_examples 'an email with suffix' do
+  before do
+    stub_config_setting(email_subject_suffix: 'Suffix')
+  end
+
+  it 'adds a correct suffix to subject' do
+    expect(subject.subject).to end_with('| Suffix')
+  end
+end
+
 RSpec.shared_examples 'an email that contains a header with author username' do
   it 'has X-GitLab-Author header containing author\'s username' do
     is_expected.to have_header 'X-GitLab-Author', user.username