[flutter_firestore_todos] authentication states

authentication_state.dart

import 'package:equatable/equatable.dart';
import 'package:meta/meta.dart';

@immutable
abstract class AuthenticationState extends Equatable {
  AuthenticationState([List props = const []]) : super(props);
}

class Uninitialized extends AuthenticationState {
  @override
  String toString() => 'Uninitialized';
}

class Authenticated extends AuthenticationState {
  final String userId;

  Authenticated(this.userId) : super([userId]);

  @override
  String toString() => 'Authenticated { userId: $userId }';
}

class Unauthenticated extends AuthenticationState {
  @override
  String toString() => 'Unauthenticated';
}