Function headless_lms_models::exercise_tasks::get_or_select_user_exercise_tasks_for_course_instance_or_exam

pub async fn get_or_select_user_exercise_tasks_for_course_instance_or_exam(
    conn: &mut PgConnection,
    user_id: Uuid,
    exercise_id: Uuid,
    course_instance_id: Option<Uuid>,
    exam_id: Option<Uuid>,
    fetch_service_info: impl Fn(Url) -> BoxFuture<'static, ModelResult<ExerciseServiceInfoApi>>
) -> ModelResult<CourseMaterialExerciseSlide>