Add util::key_error for use in key-value containers in place of std::out_of_range

libs/util/include/psemek/util/key_error.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <psemek/util/to_string.hpp>
+#include <psemek/util/type_name.hpp>
+
+#include <stdexcept>
+
+namespace psemek::util
+{
+
+	template <typename Key>
+	struct key_error
+		: std::out_of_range
+	{
+		key_error(Key const & key)
+			: std::out_of_range(to_string("unknown key ", key, " of type ", type_name<Key>()))
+			, key_(key)
+		{}
+
+		Key const & key() const noexcept
+		{
+			return key_;
+		}
+
+	private:
+		Key key_;
+	};
+
+}