Function create_page 

pub async fn create_page(
    conn: &mut PgConnection,
    course_id: Uuid,
    cms_update: CmsPageUpdate,
    author: Uuid,
    spec_fetcher: impl SpecFetcher,
    fetch_service_info: impl Fn(Url) -> BoxFuture<'static, ModelResult<ExerciseServiceInfoApi>>,
) -> ModelResult<Uuid>

Creates a new course page from a CMS update payload and returns its id.

When title or url_path are empty they are derived from the page content (the first hero-section or heading block, slugified respectively).