Adding custom fields in Prestashop checkout page (Front + Back-office)

[RaphMoreno]

Hi guys, 

I've tried looking around for answers to my issue but couldn't identify anything similar so I'm posting here in utter despair :). 

I'm creating my boutique with PS 1.7.6.4, using native theme.

I wanted to add a custom text field to the check_out page of the front-end (before payment method selection) that lets customer add the name of their 'sponsor'.

I have reached the point where I can display the textfield in the front-end and the customer can fill it, but I can't find a way to display this as a similar text field in the backend when I create a new order manually (Orders --> Orders --> Add new order). 

I guess I have to edit the AdminOrderController.php in some way so that my custom form field is added to the addorder form, and then change it again so that it writes the input in the ps_orders table, but I struggle to see where the change is needed. 

Anyone here having faced this or anyone able to guide me to find the info somewhere ? 

Thanks a lot !