added to many fields to entities author, book, recipe and ingredient

test/models/author.hpp

@@ -15,6 +15,7 @@ struct author
   std::string date_of_birth;
   unsigned short year_of_birth{};
   bool distinguished{false};
+  std::vector<matador::sql::entity<book>> books;
 
   template<typename Operator>
   void process(Operator &op)
@@ -26,6 +27,7 @@ struct author
     field::attribute(op, "date_of_birth", date_of_birth, 31);
     field::attribute(op, "year_of_birth", year_of_birth);
     field::attribute(op, "distinguished", distinguished);
+    field::has_many(op, "books", books, "author_id", "id", utils::fetch_type::LAZY);
   }
 };