Thank you so much @sunnyson for your answer !! 
This is a very clear solution !
So I tried this workaround, I have a question about it: to create an Order, do I need to create an OrderDetail first ??
I’m not sure about how to implement this, since I’ll create orders through a POST request on /orders. Should I do first a POST request on /order_details then ?
Thank you very much anyway !!