[ui][registration][models] Generate temporary url through model manager

for newly created users

beat/web/ui/registration/models.py

@@ -144,8 +144,7 @@ class RegistrationManager(models.Manager):
                         parsed_url.hostname,
                     )
 
-                    temp_url = TemporaryUrl()
-                    temp_url._generate_temporary_url(TemporaryUrl.VALIDATION, supervisiontrack)
+                    temp_url = TemporaryUrl.objects.create_temporary_url(TemporaryUrl.VALIDATION, supervisiontrack)
 
                     context = {
                         "supervisor": supervisor_user,