feat(services): add country query service

- Implement CountryQueryService for efficient country-based queries
- Add service initialization in AppDependencies class
- Include service disposal in AppDependencies dispose method
- Set default cache duration to 15 minutes

Author: fulleni

lib/src/config/app_dependencies.dart

@@ -13,6 +13,7 @@ import 'package:flutter_news_app_api_server_full_source_code/src/services/dashbo
 import 'package:flutter_news_app_api_server_full_source_code/src/services/database_seeding_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/default_user_preference_limit_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/jwt_auth_token_service.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/services/country_query_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/mongodb_rate_limit_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/mongodb_token_blacklist_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/mongodb_verification_code_storage_service.dart';
@@ -69,6 +70,7 @@ class AppDependencies {
   late final PermissionService permissionService;
   late final UserPreferenceLimitService userPreferenceLimitService;
   late final RateLimitService rateLimitService;
+  late final CountryQueryService countryQueryService;
 
   /// Initializes all application dependencies.
   ///
@@ -238,6 +240,13 @@ class AppDependencies {
         connectionManager: _mongoDbConnectionManager,
         log: Logger('MongoDbRateLimitService'),
       );
+      countryQueryService = CountryQueryService(
+        headlineRepository: headlineRepository,
+        sourceRepository: sourceRepository,
+        countryRepository: countryRepository,
+        log: Logger('CountryQueryService'),
+        cacheDuration: const Duration(minutes: 15), // Default cache duration
+      );
 
       _isInitialized = true;
       _log.info('Application dependencies initialized successfully.');
@@ -255,6 +264,7 @@ class AppDependencies {
     await _mongoDbConnectionManager.close();
     tokenBlacklistService.dispose();
     rateLimitService.dispose();
+    countryQueryService.dispose(); // Dispose the new service
     _isInitialized = false;
     _log.info('Application dependencies disposed.');
   }