pub async fn get_users_submissions_for_exercise(
    conn: &mut PgConnection,
    user_id: Uuid,
    exercise_id: Uuid,
) -> ModelResult<Vec<ExerciseSlideSubmission>>pub async fn get_users_submissions_for_exercise(
    conn: &mut PgConnection,
    user_id: Uuid,
    exercise_id: Uuid,
) -> ModelResult<Vec<ExerciseSlideSubmission>>