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/oauth.go

@@ -601,7 +601,7 @@ func (a *App) CompleteSwitchWithOAuth(service string, userData io.ReadCloser, em
 		return nil, result.Err
 	}
 
-	a.Go(func() {
+	a.Srv.Go(func() {
 		if err := a.SendSignInChangeEmail(user.Email, strings.Title(service)+" SSO", user.Locale, a.GetSiteURL()); err != nil {
 			mlog.Error(err.Error())
 		}
@@ -859,7 +859,7 @@ func (a *App) SwitchOAuthToEmail(email, password, requesterId string) (string, *
 
 	T := utils.GetUserTranslations(user.Locale)
 
-	a.Go(func() {
+	a.Srv.Go(func() {
 		if err := a.SendSignInChangeEmail(user.Email, T("api.templates.signin_change_email.body.method_email"), user.Locale, a.GetSiteURL()); err != nil {
 			mlog.Error(err.Error())
 		}