Attach existing or inline attributes (and their values) to a product.
Handles the add portion of the attribute batch engine (createAndLinkProductAttributesToProductWorkflow). Existing text/unit attributes get a new value created from value; toggle links the seeded true/false value; existing variant-axis multi_select attributes have their mirror ProductOption attached to the product with the selected value subset. Inline refs create a product-scoped attribute — axis refs also create an exclusive ProductOption — and link the values to the product.