Function upsert_added_phase 

pub async fn upsert_added_phase<E>(
    conn: &mut dyn IAsyncConnection,
    provider: &dyn IDatabaseProvider,
    db_set: &mut DbSet<E>,
    meta: &EntityTypeMeta,
) -> EFResult<usize>
where
    E: IEntityType + IEntitySnapshot + IGetKeyValues,

Phase 1b: UPSERT Added entities (is_upsert = true).