Hello, 

We want to make a custom function that, when a customer has 2 or more sales orders, create only one invoice instead of 2 (we have a workflow to create invoices automatically from sales orders that have been sent). 

I have been investigating the API documentation and I am not sure how to approach this. The main problem is that I dont see how to link more than one sales order to a invoice when I am creating it. 

When I retrieve an invoice created from 2 sales orders the JSON  has only two fields: salesorder_id and salesorder_number, but they are from only one invoice despite it was created in Books from 2 sales orders. After those fields there is a Map called salesorders with the info of the 2 that belong to that invoice. What are the rules about this structure? Which fields are mandatory and which not? Can I create a JSON with this structure and create an invoice with it?