Cookbook: How to add an action button or meta data to the product edit form

[Hocdoc]

The article https://docs.akeneo.com/latest/cookbook/ui_customization/add_a_custom_button_to_product_edit_form.html doesn't use the new CSS classes from Akeneo 1.7.

I think that the template and maybe className in export-csv.js needs an update; but I'm not sure about the new correct class names.