signIn method
账号登录统计
userId : 用户账号ID,不能为空
provider : 账号来源。如果用户通过第三方账号登录,可以传入第三方名称,如:"Weibo", "QQ" 等,可选
Implementation
Future<void> signIn(String userId, {String? provider}) async {
throw UnimplementedError('signIn() has not been implemented.');
}