Add method to retrieve currency rate by name in CurrencyController

Implemented a new method `getCurrencyRateByName` in the CurrencyController to fetch the currency rate based on the provided currency name from a JSON file. The method handles cases where the file does not exist or the currency is not found, returning appropriate JSON responses for each scenario.

app/Http/Controllers/CurrencyController.php

@@ -21,4 +21,18 @@ class CurrencyController extends Controller
 
         return response()->json(['error' => 'Veri bulunamadı'], 404);
     }
+
+    public function getCurrencyRateByName($currencyName)
+    {
+        // JSON dosyasından oku
+        if (Storage::exists('currency/today.json')) {
+            $data = json_decode(Storage::get('currency/today.json'), true);
+            if (isset($data[$currencyName])) {
+                return response()->json([$currencyName => $data[$currencyName]]);
+            }
+            return response()->json(['error' => 'Para birimi bulunamadı'], 404);
+        }
+
+        return response()->json(['error' => 'Veri bulunamadı'], 404);
+    }
 }