Adding Fields to Order API Call on WooCommerce - Stack Overflow

I am making a Rest Api call to my WooCommerce to retrieve all orders

/wp-json/wc/v3/orders

The call is perfect and I can get all the data to process on my management system.

I would like to be able to add fields to the schema to be taken from the user_meta table to complete the order placed by the user.

Can you tell me the file that generates the schema and where to add the Join to the query to retrieve the data I need?

Thank you

I tried to edit the files in rest-api/controllers/versionx.x. but without success