implemented lazy loading for object_ptr and belongs_to

include/matador/object/object_resolver_factory.hpp

@@ -0,0 +1,27 @@
+#ifndef MATADOR_OBJECT_RESOLVER_FACTORY_HPP
+#define MATADOR_OBJECT_RESOLVER_FACTORY_HPP
+
+#include "matador/object/object_resolver.hpp"
+
+#include <unordered_map>
+
+namespace matador::object {
+class object_resolver_factory {
+public:
+  virtual ~object_resolver_factory() = default;
+
+  template<class Type>
+  std::shared_ptr<object_resolver<Type>> resolver() {
+    const auto res = acquire_resolver(std::type_index(typeid(Type)));
+    if (!res) {
+      return std::dynamic_pointer_cast<object_resolver<Type>>(res);
+    }
+
+    return std::dynamic_pointer_cast<object_resolver<Type>>(res);
+  }
+
+  virtual std::shared_ptr<abstract_object_resolver> acquire_resolver(const std::type_index &type) = 0;
+  virtual void register_resolver(std::shared_ptr<abstract_object_resolver> &&resolver) = 0;
+};
+}
+#endif //MATADOR_OBJECT_RESOLVER_FACTORY_HPP