Introduce helper classes `SelfserveWashCompletionRelayValueFake`, `SelfserveWashCompletionDepartmentLaneFake`, `SelfserveWashCompletionRelayLaneFake`, and `SelfserveWashCompletionFlowHarness` to simulate relay logic for unit tests. Refactor `turnOffRelayIfConfiguredAndOn` to `turnOffRelayIfConfigured`, removing relay status pre-check for cleaner and machine relays when completing a wash session, and test associated relay actions.