Add playlist_directory to config command response

doc/protocol.rst

@@ -1599,6 +1599,7 @@ Reflection
     The following response attributes are available:
 
     - ``music_directory``: The absolute path of the music directory.
+    - ``playlist_directory``: The absolute path of the playlist directory.
 
 .. _command_commands:
 

src/command/OtherCommands.cxx

@@ -46,6 +46,7 @@
 #include "Instance.hxx"
 #include "IdleFlags.hxx"
 #include "Log.hxx"
+#include "Mapper.hxx"
 
 #ifdef ENABLE_DATABASE
 #include "DatabaseCommands.hxx"
@@ -394,6 +395,10 @@ handle_config(Client &client, [[maybe_unused]] Request args, Response &r)
 	}
 #endif
 
+	const auto spl_path = map_spl_path();
+	if (!spl_path.IsNull())
+		r.Fmt(FMT_STRING("playlist_directory: {}\n"), spl_path.ToUTF8());
+
 	return CommandResult::OK;
 }