pub async fn get_course_material_exercise(
conn: &mut PgConnection,
user_id: Option<Uuid>,
exercise_id: Uuid,
fetch_service_info: impl Fn(Url) -> BoxFuture<'static, ModelResult<ExerciseServiceInfoApi>>,
file_store: &dyn FileStore,
app_conf: &ApplicationConfiguration,
) -> ModelResult<CourseMaterialExercise>