added initial draft of inbox

lib/core/service/paperless_statistics_service.dart

@@ -0,0 +1,29 @@
+import 'dart:convert';
+
+import 'package:http/http.dart';
+import 'package:injectable/injectable.dart';
+import 'package:paperless_mobile/core/model/error_message.dart';
+import 'package:paperless_mobile/core/model/paperless_statistics.dart';
+import 'package:paperless_mobile/core/type/types.dart';
+
+abstract class PaperlessStatisticsService {
+  Future<PaperlessStatistics> getStatistics();
+}
+
+@Injectable(as: PaperlessStatisticsService)
+class PaperlessStatisticsServiceImpl extends PaperlessStatisticsService {
+  final BaseClient client;
+
+  PaperlessStatisticsServiceImpl(@Named('timeoutClient') this.client);
+
+  @override
+  Future<PaperlessStatistics> getStatistics() async {
+    final response = await client.get(Uri.parse('/api/statistics/'));
+    if (response.statusCode == 200) {
+      return PaperlessStatistics.fromJson(
+        jsonDecode(utf8.decode(response.bodyBytes)) as JSON,
+      );
+    }
+    throw const ErrorMessage.unknown();
+  }
+}