feat: add feature flag for URA (#6593)

src/components/FeatureFlagModal/FeatureFlagModal.tsx

 import { BaseVariant, FeatureFlag, featureFlagSettings, useUpdateFlag } from 'featureFlags'
 import { DetailsV2Variant, useDetailsV2Flag } from 'featureFlags/flags/nftDetails'
 import { TraceJsonRpcVariant, useTraceJsonRpcFlag } from 'featureFlags/flags/traceJsonRpc'
+import { UnifiedRouterVariant, useUnifiedRoutingAPIFlag } from 'featureFlags/flags/unifiedRouter'
 import { useUpdateAtom } from 'jotai/utils'
 import { Children, PropsWithChildren, ReactElement, ReactNode, useCallback, useState } from 'react'
 import { X } from 'react-feather'
@@ -207,6 +208,12 @@ export default function FeatureFlagModal() {
         featureFlag={FeatureFlag.detailsV2}
         label="Use the new details page for nfts"
       />
+      <FeatureFlagOption
+        variant={UnifiedRouterVariant}
+        value={useUnifiedRoutingAPIFlag()}
+        featureFlag={FeatureFlag.uraEnabled}
+        label="Enable the Unified Routing API"
+      />
       <FeatureFlagGroup name="Debug">
         <FeatureFlagOption
           variant={TraceJsonRpcVariant}

src/featureFlags/flags/featureFlags.ts

@@ -6,4 +6,5 @@ export enum FeatureFlag {
   permit2 = 'permit2',
   fiatOnRampButtonOnSwap = 'fiat_on_ramp_button_on_swap_page',
   detailsV2 = 'details_v2',
+  uraEnabled = 'ura_enabled',
 }

src/featureFlags/flags/unifiedRouter.ts

+import { BaseVariant, FeatureFlag, useBaseFlag } from '../index'
+
+export function useUnifiedRoutingAPIFlag(): BaseVariant {
+  return useBaseFlag(FeatureFlag.uraEnabled)
+}
+
+// eslint-disable-next-line import/no-unused-modules
+export function useUnifiedRoutingAPIEnabled(): boolean {
+  return useUnifiedRoutingAPIFlag() === BaseVariant.Enabled
+}
+
+export { BaseVariant as UnifiedRouterVariant }