object: add destroy method for owned types

object.hpp

@@ -38,7 +38,7 @@ namespace cruft::vk {
         const id_t& id (void) const&;
         id_t& id (void) &;
 
-    private:
+    protected:
         id_t m_id;
     };
 
@@ -117,13 +117,31 @@ namespace cruft::vk {
     template <typename SelfT, typename OwnerT>
     struct owned : public object<SelfT> {
         using id_t = typename object<SelfT>::id_t;
+        using owner_t = OwnerT;
+
         using object<SelfT>::object;
 
+
         template <typename ...Args>
         owned (Args &&...args):
             object<SelfT> (make (std::forward<Args> (args)...))
         { ; }
 
+
+        ~owned ()
+        {
+            CHECK_EQ (this->id (), VK_NULL_HANDLE);
+        }
+
+
+        void
+        destroy (OwnerT &parent)
+        {
+            life_traits<SelfT>::destroy (parent.id (), this->id (), nullptr);
+            this->m_id = VK_NULL_HANDLE;
+        }
+
+
     private:
         template <typename ...Args>
         static