Cleanup Snapclient includes

client/metadata.hpp

@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef METADATA_H
-#define METADATA_H
+#pragma once
 
+// local headers
 #include "common/json.hpp"
 
+// standard headers
+#include <iostream>
+
+
 // Prefix used in output
 #define METADATA std::string("metadata")
 
@@ -99,5 +103,3 @@ public:
         return 0;
     }
 };
-
-#endif