MM-12849 Moving all non request scoped items to Server struct (#9806)

* Moving goroutine pool

* Auto refactor

* Moving plugins.

* Auto refactor

* Moving fields to server

* Auto refactor

* Removing siteurl duplication.

* Moving reset of app fields

* Auto refactor

* Formatting

* Moving niling of Server to after last use

* Fixing unit tests.

app/notification_email.go

@@ -103,7 +103,7 @@ func (a *App) sendNotificationEmail(notification *postNotification, user *model.
 	teamURL := a.GetSiteURL() + "/" + team.Name
 	var bodyText = a.getNotificationEmailBody(user, post, channel, channelName, senderName, team.Name, teamURL, emailNotificationContentsType, useMilitaryTime, translateFunc)
 
-	a.Go(func() {
+	a.Srv.Go(func() {
 		if err := a.SendMail(user.Email, html.UnescapeString(subjectText), bodyText); err != nil {
 			mlog.Error(fmt.Sprint("Error to send the email", user.Email, err))
 		}