Function insert_new_content_page

pub async fn insert_new_content_page(
    conn: &mut PgConnection,
    new_page: NewPage,
    user: Uuid,
    spec_fetcher: impl SpecFetcher,
    fetch_service_info: impl Fn(Url) -> BoxFuture<'static, ModelResult<ExerciseServiceInfoApi>>,
) -> ModelResult<Page>