고객사 목록 쿼리스트링 연동 및 공통 JSON 파서 도입

lib/features/util/postal_search/data/dtos/postal_code_dto.dart

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+import 'package:superport_v2/core/common/utils/json_utils.dart';
+
+import '../../domain/entities/postal_code.dart';
+
+/// 우편번호 검색 API 응답을 표현하는 DTO.
+class PostalCodeDto {
+  PostalCodeDto({
+    required this.zipcode,
+    this.sido,
+    this.sigungu,
+    this.roadName,
+    this.buildingMainNo,
+    this.buildingSubNo,
+  });
+
+  final String zipcode;
+  final String? sido;
+  final String? sigungu;
+  final String? roadName;
+  final int? buildingMainNo;
+  final int? buildingSubNo;
+
+  factory PostalCodeDto.fromJson(Map<String, dynamic> json) {
+    return PostalCodeDto(
+      zipcode: json['zipcode'] as String,
+      sido: json['sido'] as String?,
+      sigungu: json['sigungu'] as String?,
+      roadName: json['road_name'] as String?,
+      buildingMainNo: _parseInt(json['building_main_no']),
+      buildingSubNo: _parseInt(json['building_sub_no']),
+    );
+  }
+
+  PostalCode toEntity() {
+    return PostalCode(
+      zipcode: zipcode,
+      sido: sido,
+      sigungu: sigungu,
+      roadName: roadName,
+      buildingMainNo: buildingMainNo,
+      buildingSubNo: buildingSubNo,
+    );
+  }
+
+  static List<PostalCode> fromResponse(dynamic data) {
+    final items = JsonUtils.extractList(data, keys: const ['items', 'data']);
+    if (items.isEmpty) {
+      return const [];
+    }
+    return items
+        .map(PostalCodeDto.fromJson)
+        .map((dto) => dto.toEntity())
+        .toList(growable: false);
+  }
+}
+
+int? _parseInt(Object? value) {
+  if (value == null) {
+    return null;
+  }
+  if (value is int) {
+    return value;
+  }
+  if (value is String) {
+    return int.tryParse(value);
+  }
+  return null;
+}