implement scrap and ship skeleton

src/lib/sim/ScrapSystem.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <functional>
+#include <vector>
+
+#include <QVector2D>
+
+#include "EntityId.h"
+#include "Scrap.h"
+#include "Tick.h"
+
+class ScrapSystem
+{
+public:
+    explicit ScrapSystem(std::function<EntityId()> allocateId);
+
+    EntityId spawn(QVector2D position, int amount, Tick despawnAt);
+    void     tickDespawn(Tick currentTick);
+
+    const Scrap*       findScrap(EntityId id) const;
+    std::vector<Scrap> allScraps()            const;
+
+private:
+    std::function<EntityId()> m_allocateId;
+    std::vector<Scrap>        m_scraps;
+};