Send notification emails to the "project", and put people in Cc

This fixes email threading in Mail.app, that doesn't like when a thread
doesn't have stable recipients.

For instance, here is a possible sender-recipient combinations before:

From: A
To: Me
New issue

From: B
To: Me
Reply on new issue

From: A
To: Me
Another reply

Mail.app doesn't see B as a participant to the original email thread,
and decides to break the thread: it will group all messages from A
together, and separately all messages from B.

This commit makes the thread look like this:

From: A
To: gitlab/project
Cc: Me
New issue

From: B
To: gitlab/project
Cc: Me
Reply on new issue

From: A
To: gitlab/project
Cc: Me
Another reply

Mail.app sees a common recipient, and group the thread correctly.

1 files changed, 4 insertions, 4 deletions

diff --git a/app/mailers/emails/merge_requests.rb b/app/mailers/emails/merge_requests.rb
index ea5671c4502..6b46cc90e08 100644
--- a/app/mailers/emails/merge_requests.rb
+++ b/app/mailers/emails/merge_requests.rb
@@ -6,7 +6,7 @@ module Emails
       @target_url = project_merge_request_url(@project, @merge_request)
       set_message_id("merge_request_#{merge_request_id}")
       mail(from: sender(@merge_request.author_id),
-           to: recipient(recipient_id),
+           cc: recipient(recipient_id),
            subject: subject("#{@merge_request.title} (##{@merge_request.iid})"))
     end
 
@@ -17,7 +17,7 @@ module Emails
       @target_url = project_merge_request_url(@project, @merge_request)
       set_reference("merge_request_#{merge_request_id}")
       mail(from: sender(updated_by_user_id),
-           to: recipient(recipient_id),
+           cc: recipient(recipient_id),
            subject: subject("#{@merge_request.title} (##{@merge_request.iid})"))
     end
 
@@ -28,7 +28,7 @@ module Emails
       @target_url = project_merge_request_url(@project, @merge_request)
       set_reference("merge_request_#{merge_request_id}")
       mail(from: sender(updated_by_user_id),
-           to: recipient(recipient_id),
+           cc: recipient(recipient_id),
            subject: subject("#{@merge_request.title} (##{@merge_request.iid})"))
     end
 
@@ -38,7 +38,7 @@ module Emails
       @target_url = project_merge_request_url(@project, @merge_request)
       set_reference("merge_request_#{merge_request_id}")
       mail(from: sender(updated_by_user_id),
-           to: recipient(recipient_id),
+           cc: recipient(recipient_id),
            subject: subject("#{@merge_request.title} (##{@merge_request.iid})"))
     end
   end