refactor: extract rate formatting logic to RateService and add tests

app/Http/Controllers/RateController.php

@@ -4,31 +4,16 @@ namespace App\Http\Controllers;
 
 use App\Models\City;
 use App\Models\Rate;
+use App\Services\RateService;
 
 class RateController extends Controller
 {
-    public function __invoke()
+    public function __invoke( RateService $rateService)
     {
+        $rates = $rateService->getFormattedRates();
 
-        $supportedCities = City::query()
-            ->whereIn('name', City::supportedCities())
-            ->get()
-            ->sortByDesc(fn ($city) => $city->name === 'sanaa')
-            ->values();
-
-        $rates = Rate::query()
-            ->with('currency', 'city')
-            ->orderBy('city_id', 'asc')
-            ->orderBy('currency_id', 'asc')
-            ->orderBy('date', 'desc')
-            ->get()
-            ->groupBy(fn ($rate) => $rate->city_id.'-'.$rate->currency_id)
-            ->map(fn ($group) => $group->first())
-            ->groupBy('city_id');
-
-        return view('rates', [
-            'rates' => $rates,
-            'supportedCities' => $supportedCities,
+        return view('rates', [  
+            'rates' => $rates,  
         ]);
     }
 }