Codechange: Check command callbacks registration even in single player

src/network/network_command.cpp

@@ -111,6 +111,16 @@ inline auto MakeCallbackTable(std::index_sequence<i...>) noexcept
 /** Type-erased table of callbacks. */
 static const auto _callback_table = MakeCallbackTable(std::make_index_sequence<_callback_tuple_size>{});
 
+/**
+ * Helper function to ensure that callbacks used when Posting commands are actually registered for the network calls.
+ * @param callback The callback to check.
+ * @return \c true when the callback is in the callback table, otherwise \c false.
+ */
+bool IsNetworkRegisteredCallback(CommandCallback *callback)
+{
+	return std::ranges::find(_callback_table, callback) != _callback_table.end();
+}
+
 template <typename T> struct CallbackArgsHelper;
 template <typename... Targs>
 struct CallbackArgsHelper<void(*const)(Commands, const CommandCost &, Targs...)> {