stabilized logger classes

test/models/student.hpp

@@ -5,6 +5,7 @@
 #include "matador/utils/foreign_attributes.hpp"
 
 #include "matador/object/object_ptr.hpp"
+#include "matador/object/collection.hpp"
 #include "matador/object/many_to_many_relation.hpp"
 
 #include <utility>
@@ -16,7 +17,7 @@ struct course;
 struct student {
   unsigned int id{};
   std::string name;
-  std::vector<object::object_ptr<course> > courses;
+  object::collection<object::object_ptr<course> > courses;
 
   student() = default;
 
@@ -37,7 +38,7 @@ struct student {
 struct course {
   unsigned int id{};
   std::string title;
-  std::vector<object::object_ptr<student> > students;
+  object::collection<object::object_ptr<student> > students;
 
   course() = default;