refactor(country): implement specialized filtering for country model

- Replace generic DataRepository readAll method with CountryService for country model
- Add support for 'usage' filter in country data operation
- Return PaginatedResponse to maintain consistency with generic API structure
- Remove unnecessary parameters (uid, s, p) from the custom operation

Author: fulleni

lib/src/registry/data_operation_registry.dart

@@ -2,6 +2,7 @@ import 'package:core/core.dart';
 import 'package:dart_frog/dart_frog.dart';
 import 'package:data_repository/data_repository.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/middlewares/ownership_check_middleware.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/services/country_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/dashboard_summary_service.dart';
 
 // --- Typedefs for Data Operations ---
@@ -128,12 +129,19 @@ class DataOperationRegistry {
         sort: s,
         pagination: p,
       ),
-      'country': (c, uid, f, s, p) => c.read<DataRepository<Country>>().readAll(
-        userId: uid,
-        filter: f,
-        sort: s,
-        pagination: p,
-      ),
+      'country': (c, uid, f, s, p) async {
+        // For 'country' model, delegate to CountryService for specialized filtering.
+        // The CountryService handles the 'usage' filter and returns a List<Country>.
+        // We then wrap this list in a PaginatedResponse for consistency with
+        // the generic API response structure.
+        final countryService = c.read<CountryService>();
+        final countries = await countryService.getCountries(f);
+        return PaginatedResponse<Country>(
+          items: countries,
+          cursor: null, // No cursor for this type of filtered list
+          hasMore: false, // No more items as it's a complete filtered set
+        );
+      },
       'language': (c, uid, f, s, p) => c
           .read<DataRepository<Language>>()
           .readAll(userId: uid, filter: f, sort: s, pagination: p),