Fix cart line attributes being dropped and userErrors not logged

[lwekuiper]

Two small bugs in the cart JS, both in the same add-to-cart path.

updateFromResponse() builds the line item attributes with attrs[key] = attr.value, but key is never defined in that scope. Under a bundler this throws a ReferenceError in strict mode, and otherwise it writes to a global, so line attributes never reach $store['statamic.shopify.cart'].lineItems. This is what you get back from cartLinesAdd when you pass attributes, so any custom line data (we use it for shirt name and number personalisation) is lost when the cart re-renders.

- line.attributes.forEach((attr) => attrs[key] = attr.value);
+ line.attributes.forEach((attr) => attrs[attr.key] = attr.value);

The second one is in addLines(): the userErrors branch logs errors from the destructured response instead of the user errors it just checked, so the warning is always empty at the point where it would be most useful.

  if (data.cartLinesAdd.userErrors.length > 0) {
-     console.warn(errors);
+     console.warn(data.cartLinesAdd.userErrors);

Both are in the published JS, so they only reach apps after a re-publish.

[ryanmitchell]

Good spot, thank you for both.