curl -k -u admin:changeme https://localhost/foreman/api/config_templates/4/ -X PUT -H 'Accept: version=2' -H 'Content-Type: application/json' \
-d '{"config_template":{"operatingsystem_ids":[1]}}'

{
  "config_template": {
    "errors": {
      "base": [
        "You do not have permission to edit this template" 
      ]
    },
    "id": 4,
    "full_messages": [
      "You do not have permission to edit this template" 
    ]
  }
}