MM-19867: - Implement allowing multiple SAML Libraries (#13299)

* Implement allowing multiple SAML Libraries

* fix unit tests

* updates based on review feedback

* Only set on startup, not config changes

* update unit tests, reload enterprise

* need to reset for previous tests

* update license statement

* fix licensing line

app/enterprise.go

@@ -107,6 +107,12 @@ func RegisterSamlInterface(f func(*App) einterfaces.SamlInterface) {
 	samlInterface = f
 }
 
+var samlInterfaceNew func(*App) einterfaces.SamlInterface
+
+func RegisterNewSamlInterface(f func(*App) einterfaces.SamlInterface) {
+	samlInterfaceNew = f
+}
+
 var notificationInterface func(*App) einterfaces.NotificationInterface
 
 func RegisterNotificationInterface(f func(*App) einterfaces.NotificationInterface) {
@@ -136,7 +142,13 @@ func (s *Server) initEnterprise() {
 		s.Notification = notificationInterface(s.FakeApp())
 	}
 	if samlInterface != nil {
-		s.Saml = samlInterface(s.FakeApp())
+		if *s.FakeApp().Config().ExperimentalSettings.UseNewSAMLLibrary && samlInterfaceNew != nil {
+			mlog.Debug("Loading new SAML2 library")
+			s.Saml = samlInterfaceNew(s.FakeApp())
+		} else {
+			mlog.Debug("Loading original SAML library")
+			s.Saml = samlInterface(s.FakeApp())
+		}
 		s.AddConfigListener(func(_, cfg *model.Config) {
 			if err := s.Saml.ConfigureSP(); err != nil {
 				mlog.Error("An error occurred while configuring SAML Service Provider", mlog.Err(err))