Function update_by_id_in_parent_context 

pub async fn update_by_id_in_parent_context(
    conn: &mut PgConnection,
    page_update: PageUpdateArgs,
    expected_course_id: Option<Uuid>,
    expected_exam_id: Option<Uuid>,
    expected_updated_at: Option<DateTime<Utc>>,
    spec_fetcher: impl SpecFetcher,
    fetch_service_info: impl Fn(Url) -> BoxFuture<'static, ModelResult<ExerciseServiceInfoApi>>,
) -> ModelResult<ContentManagementPage>

With expected_updated_at set, refuses with ModelErrorType::StaleVersion unless the page row still has that updated_at. The check runs under the page row lock.