feat: add references header to reply emails (#11719)

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

spec/mailboxes/reply_mailbox_spec.rb

@@ -12,7 +12,7 @@ RSpec.describe ReplyMailbox do
     let(:conversation) { create(:conversation, assignee: agent, inbox: create(:inbox, account: account, greeting_enabled: false), account: account) }
     let(:described_subject) { described_class.receive reply_mail }
     let(:serialized_attributes) do
-      %w[bcc cc content_type date from html_content in_reply_to message_id multipart number_of_attachments subject text_content to]
+      %w[bcc cc content_type date from html_content in_reply_to message_id multipart number_of_attachments references subject text_content to]
     end
 
     context 'with reply uuid present' do

spec/mailboxes/support_mailbox_spec.rb

@@ -55,7 +55,7 @@ RSpec.describe SupportMailbox do
     let(:support_in_reply_to_mail) { create_inbound_email_from_fixture('support_in_reply_to.eml') }
     let(:described_subject) { described_class.receive support_mail }
     let(:serialized_attributes) do
-      %w[bcc cc content_type date from html_content in_reply_to message_id multipart number_of_attachments subject
+      %w[bcc cc content_type date from html_content in_reply_to message_id multipart number_of_attachments references subject
          text_content to]
     end
     let(:conversation) { Conversation.where(inbox_id: channel_email.inbox).last }
@@ -111,6 +111,29 @@ RSpec.describe SupportMailbox do
       end
     end
 
+    describe 'email with references header' do
+      let(:mail_with_references) { create_inbound_email_from_fixture('mail_with_references.eml') }
+      let(:described_subject) { described_class.receive mail_with_references }
+
+      before do
+        # reuse the existing channel_email that's already set to 'care@example.com'
+        described_subject
+      end
+
+      it 'includes references in the message content_attributes' do
+        message = conversation.messages.last
+        email_attributes = message.content_attributes['email']
+
+        expect(email_attributes['references']).to be_present
+        expect(email_attributes['references']).to eq(['4e6e35f5a38b4_479f13bb90078178@small-app-01.mail', 'test-reference-id'])
+      end
+
+      it 'includes references in serialized email attributes' do
+        message = conversation.messages.last
+        expect(message.content_attributes['email'].keys).to include('references')
+      end
+    end
+
     describe 'Sender without name' do
       let(:support_mail_without_sender_name) { create_inbound_email_from_fixture('support_without_sender_name.eml') }
       let(:described_subject) { described_class.receive support_mail_without_sender_name }