Allow customers to add arbitrary data to products when adding to cart I've got a product type called workshop and I want customers to be able to specify the names of their kids when they add a workshop to the cart. If I could figure out how to add any arbitrary data at all I'm sure I could carry this through to where I ultimately want it to be, which is that the arbitrary data would actually be a choice of some number of Paragraph entities referenced by their user profile, but all the solutions I have been able to find seem to be for Drupal 7, so I'm dead in the water. 

Any suggestions?
For the benefit of anyone who comes looking, the answer is that the fields need to be added to the order item type. Commerce sees each product as a sort of Platonic object and stamps out instances as order items -- think line items. You can add fields to this. Whee. Unfortunately, you can't reference Paragraph entities because, as ridiculous as it seems to me, Paragraph entities only support a single reference.