Slim down `ndncert-common.hpp`
Change-Id: Ifba0966d3787c5cbf770963b82cba054ee1fe791
diff --git a/src/detail/ca-request-state.hpp b/src/detail/ca-request-state.hpp
index a11caf0..49fa583 100644
--- a/src/detail/ca-request-state.hpp
+++ b/src/detail/ca-request-state.hpp
@@ -1,6 +1,6 @@
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
- * Copyright (c) 2017-2023, Regents of the University of California.
+ * Copyright (c) 2017-2024, Regents of the University of California.
*
* This file is part of ndncert, a certificate management system based on NDN.
*
@@ -24,6 +24,7 @@
#include "detail/ndncert-common.hpp"
#include <array>
+#include <optional>
namespace ndncert {