Make customUnitRateID optional and apply Prettier to tests

The duplicate-policy clone helper already treated newDefaultRateID as
optional at runtime; mirror that in the parameter type so callers that
don't have a rate ID (existing unit tests for per-diem-only paths) can
pass through without an explicit pass-through. No production-call-site
behavior change — buildDuplicatePolicyData still always provides it.

Author: wildan-m

src/libs/PolicyUtils.ts

@@ -335,7 +335,7 @@ function getCustomUnitsForDuplication(
     customUnitIDs: {
         distanceCustomUnitID: string;
         perDiemCustomUnitID: string;
-        customUnitRateID: string;
+        customUnitRateID?: string;
     },
 ): Record<string, CustomUnit> | undefined {
     const customUnits = policy?.customUnits;

tests/unit/PolicyUtilsTest.ts

@@ -370,7 +370,11 @@ describe('PolicyUtils', () => {
                 ...createRandomPolicy(0),
                 customUnits: {[distanceUnitWithMultipleRates.customUnitID]: distanceUnitWithMultipleRates},
             };
-            const result = getCustomUnitsForDuplication(policyWithMultipleRates, true, false, {distanceCustomUnitID: 'newDist', perDiemCustomUnitID: 'newPerDiem', customUnitRateID: 'newRate'});
+            const result = getCustomUnitsForDuplication(policyWithMultipleRates, true, false, {
+                distanceCustomUnitID: 'newDist',
+                perDiemCustomUnitID: 'newPerDiem',
+                customUnitRateID: 'newRate',
+            });
             expect(result).toEqual({
                 newDist: {
                     ...distanceUnitWithMultipleRates,