DEV: Add SMTP group ID to EmailLog (#13381)

Adds a new `smtp_group_id` column to `EmailLog` which is filled in if the mail `from_address` matches a group's `email_username`. This is for easier debugging, so we know which emails have been sent via group SMTP.

spec/components/email/sender_spec.rb

@@ -337,6 +337,36 @@ describe Email::Sender do
         expect(email_log.to_address).to eq('eviltrout@test.domain')
         expect(email_log.user_id).to be_blank
       end
+
+      context 'when the email is sent using group SMTP credentials' do
+        let(:reply) { Fabricate(:post, topic: post.topic, reply_to_user: post.user, reply_to_post_number: post.post_number) }
+        let(:notification) { Fabricate(:posted_notification, user: post.user, post: reply) }
+        let(:message) do
+          UserNotifications.user_private_message(
+            post.user,
+            post: reply,
+            notification_type: notification.notification_type,
+            notification_data_hash: notification.data_hash
+          )
+        end
+        let(:group) { Fabricate(:smtp_group) }
+
+        before do
+          SiteSetting.enable_smtp = true
+        end
+
+        it 'adds the group id to the email log' do
+          TopicAllowedGroup.create(topic: post.topic, group: group)
+
+          email_sender.send
+
+          expect(email_log).to be_present
+          expect(email_log.email_type).to eq('valid_type')
+          expect(email_log.to_address).to eq(post.user.email)
+          expect(email_log.user_id).to be_blank
+          expect(email_log.smtp_group_id).to eq(group.id)
+        end
+      end
     end
 
     context "email log with a post id and topic id" do