implemented user service (no auth!)

backend-dart/lib/application/repository/provider.dart

@@ -0,0 +1,9 @@
+import 'package:backend_dart/application/repository/user_repository_impl.dart';
+import 'package:backend_dart/domain/repository/user_repository.dart';
+import 'package:backend_dart/infrastructure/persistence/database_provider.dart';
+import 'package:riverpod/riverpod.dart';
+
+final userRepoProvider = Provider<UserRepository>((ref) {
+  final database = ref.read(databaseProvider);
+  return UserRepositoryImpl(database);
+});

backend-dart/lib/application/repository/user_repository_impl.dart

@@ -0,0 +1,45 @@
+import 'package:backend_dart/domain/entities/user.dart';
+import 'package:backend_dart/domain/interface/database.dart';
+import 'package:backend_dart/domain/interface/error.dart';
+import 'package:backend_dart/domain/repository/user_repository.dart';
+import 'package:fpdart/fpdart.dart';
+
+class UserRepositoryImpl implements UserRepository {
+  final IDatabase database;
+  UserRepositoryImpl(this.database);
+
+  @override
+  TaskEither<IError, User> create(User user) {
+    return database.users
+        .generateId()
+        .map(
+          (id) => user.copyWith(id: id),
+        )
+        .flatMap(database.users.create);
+  }
+
+  @override
+  TaskEither<IError, User> findByEmail(String email) {
+    return database.users.findByEmail(email);
+  }
+
+  @override
+  TaskEither<IError, User> findById(String id) {
+    return database.users.findById(id);
+  }
+
+  @override
+  TaskEither<IError, User> update(User user) {
+    return database.users.update(user);
+  }
+
+  @override
+  TaskEither<IError, void> delete(String id) {
+    return database.users.delete(id);
+  }
+
+  @override
+  TaskEither<IError, List<User>> findAll() {
+    return database.users.findAll();
+  }
+}