Add List-Unsubscribe email header (#26085)

spec/mailers/notification_mailer_spec.rb

@@ -3,21 +3,42 @@
 require 'rails_helper'
 
 RSpec.describe NotificationMailer do
-  let(:receiver)       { Fabricate(:user) }
+  let(:receiver)       { Fabricate(:user, account_attributes: { username: 'alice' }) }
   let(:sender)         { Fabricate(:account, username: 'bob') }
   let(:foreign_status) { Fabricate(:status, account: sender, text: 'The body of the foreign status') }
   let(:own_status)     { Fabricate(:status, account: receiver.account, text: 'The body of the own status') }
 
+  shared_examples 'headers' do |type, thread|
+    it 'renders the to and from headers' do
+      expect(mail[:to].value).to eq "#{receiver.account.username} <#{receiver.email}>"
+      expect(mail.from).to eq ['notifications@localhost']
+    end
+
+    it 'renders the list headers' do
+      expect(mail['List-ID'].value).to eq "<#{type}.alice.cb6e6126.ngrok.io>"
+      expect(mail['List-Unsubscribe'].value).to match(%r{<https://cb6e6126.ngrok.io/unsubscribe\?token=.+>})
+      expect(mail['List-Unsubscribe'].value).to match("&type=#{type}")
+      expect(mail['List-Unsubscribe-Post'].value).to eq 'List-Unsubscribe=One-Click'
+    end
+
+    if thread
+      it 'renders the thread headers' do
+        expect(mail['In-Reply-To'].value).to match(/<conversation-\d+.\d\d\d\d-\d\d-\d\d@cb6e6126.ngrok.io>/)
+        expect(mail['References'].value).to match(/<conversation-\d+.\d\d\d\d-\d\d-\d\d@cb6e6126.ngrok.io>/)
+      end
+    end
+  end
+
   describe 'mention' do
     let(:mention) { Mention.create!(account: receiver.account, status: foreign_status) }
     let(:notification) { Notification.create!(account: receiver.account, activity: mention) }
     let(:mail) { prepared_mailer_for(receiver.account).mention }
 
     include_examples 'localized subject', 'notification_mailer.mention.subject', name: 'bob'
+    include_examples 'headers', 'mention', true
 
-    it 'renders the headers' do
+    it 'renders the subject' do
       expect(mail.subject).to eq('You were mentioned by bob')
-      expect(mail[:to].value).to eq("#{receiver.account.username} <#{receiver.email}>")
     end
 
     it 'renders the body' do
@@ -32,10 +53,10 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(receiver.account).follow }
 
     include_examples 'localized subject', 'notification_mailer.follow.subject', name: 'bob'
+    include_examples 'headers', 'follow', false
 
-    it 'renders the headers' do
+    it 'renders the subject' do
       expect(mail.subject).to eq('bob is now following you')
-      expect(mail[:to].value).to eq("#{receiver.account.username} <#{receiver.email}>")
     end
 
     it 'renders the body' do
@@ -49,10 +70,10 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(own_status.account).favourite }
 
     include_examples 'localized subject', 'notification_mailer.favourite.subject', name: 'bob'
+    include_examples 'headers', 'favourite', true
 
-    it 'renders the headers' do
+    it 'renders the subject' do
       expect(mail.subject).to eq('bob favorited your post')
-      expect(mail[:to].value).to eq("#{receiver.account.username} <#{receiver.email}>")
     end
 
     it 'renders the body' do
@@ -67,10 +88,10 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(own_status.account).reblog }
 
     include_examples 'localized subject', 'notification_mailer.reblog.subject', name: 'bob'
+    include_examples 'headers', 'reblog', true
 
-    it 'renders the headers' do
+    it 'renders the subject' do
       expect(mail.subject).to eq('bob boosted your post')
-      expect(mail[:to].value).to eq("#{receiver.account.username} <#{receiver.email}>")
     end
 
     it 'renders the body' do
@@ -85,10 +106,10 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(receiver.account).follow_request }
 
     include_examples 'localized subject', 'notification_mailer.follow_request.subject', name: 'bob'
+    include_examples 'headers', 'follow_request', false
 
-    it 'renders the headers' do
+    it 'renders the subject' do
       expect(mail.subject).to eq('Pending follower: bob')
-      expect(mail[:to].value).to eq("#{receiver.account.username} <#{receiver.email}>")
     end
 
     it 'renders the body' do