Refactor database layer: convert to DatabaseProvider class with initialization

bin/routes/user_routes.dart

@@ -0,0 +1,54 @@
+import 'package:shelf/shelf.dart';
+import 'package:shelf_router/shelf_router.dart';
+import '../database/database_provider.dart';
+import 'dart:convert';
+
+class UserRoutes {
+  final DatabaseProvider database;
+
+  UserRoutes(this.database);
+
+  Router get routes {
+    final router = Router();
+    router.get('/user', _getAllUsers);
+    router.post('/user', _createUser);
+    router.put('/user/<id>', _updateUser);
+    router.delete('/user/<id>', _deleteUser);
+    return router;
+  }
+
+  Future<Response> _getAllUsers(Request request) async {
+    final users = await database.getAllUsers();
+    return Response(200, body: jsonEncode(users.map((u) => u.toMap()).toList()));
+  }
+
+  Future<Response> _createUser(Request request) async {
+    final body = await request.readAsString();
+    final data = jsonDecode(body);
+
+    final login = data['login'];
+    final password = data['password'];
+
+    final user = await database.createUser(login, password);
+    return Response(201, body: jsonEncode(user.toMap()));
+  }
+
+  Future<Response> _updateUser(Request request) async {
+    final id = int.parse(request.params['id']!);
+
+    final body = await request.readAsString();
+    final data = jsonDecode(body);
+
+    final login = data['login'];
+    final password = data['password'];
+
+    final user = await database.updateUser(id, login, password);
+    return Response(200, body: jsonEncode(user.toMap()));
+  }
+
+  Future<Response> _deleteUser(Request request) async {
+    final id = int.parse(request.params['id']!);
+    await database.deleteUser(id);
+    return Response(204);
+  }
+}