Update REST API classes to remove extraneous wrapper classes

Much of the REST API model has "Root" classes which are just wrappers to handle the name of a JSON node.

I think we can get rid of all of those, by defining the actual model classes with a couple JSON annotations. An example is the Webhook class:

@JsonTypeName(value = "webhook")
@JsonTypeInfo(include = JsonTypeInfo.As.WRAPPER_OBJECT, use = JsonTypeInfo.Id.NAME)

Update:

This is trickier than expected. The main approach works fine for single item use, but causes issues when there's an array of items being mapped to a collection.

For example, for a single Product call, Shopify returns something like:

{
"product": {
"id": 632910392,
"title": "IPod Nano - 8GB",
"body_html": "

It's the small iPod......

Which is why we need the Product class to have the As.WRAPPER_OBJECT annotation (or the wrapper class).

However, when getting an array of products, Shopify sends in something like this:

{
"products": [
{
"id": 632910392,
"title": "IPod Nano - 8GB",
"body_html": "

It's the small iPo

Note the lack of "product" level nodes. That's what breaks here. So basically we want Product to wrap itself with a "product" node if it's a single Product, but to NOT wrap itself when its an array or collection. I can't find any easy way to do this. A custom de-serializer is an option, but I'm not sure that's a lot better/cleaner than these wrapper classes....

Beginnen Sie mit den REST API-Modellklassen, einschließlich Webhook und Product, und vergleichen Sie, wie Jackson-Wrapper-Annotationen einzelne Objekte gegenüber Sammlungen behandeln. Reproduzieren Sie die dokumentierten Product- und products-Antwortformen und ermitteln Sie anschließend, ob die Root-Wrapper entfernt werden können, wobei beide Deserialisierungsformen erhalten bleiben; das Issue nennt keine bestimmten Dateien oder Tests.