Creates or updates pay rates for one or more users. If a pay rate exists for the same effective date, it is replaced; otherwise, a new entry is added to the pay rate history. The effective date cannot be on or after any approved or locked timesheet days. If such days exist, the request fails with HAS_LOCKED_DAYS. For bulk requests with resource rates enabled, the system validates user eligibility and tracks all changes. When isResourceRateEnabled is true, resourcesRates must include all resources with custom rates.