enrichAccessLogsWithUsers preferred the UserService contract over the local
repository — correct layering, but it looped GetUserByID and issued up to a
page-size worth of separate SELECTs against w_users, while the single-query
WHERE id IN variant was only reached in the no-contract fallback branch.
Give the contract a GetUsersByIDs so callers can keep the layering and drop
the N+1. The test asserts 1 query batched against 3 per-id, so the counting
itself is checked.
ryan