Add support for WP-API error parsing

[koke]

Closes: #8030

Description

The existing networking code uses DotcomValidator and DotcomError to attempt to extract error information from WordPress.com API responses (error/message). However, the newer endpoints that use the core REST API (wpcom/v2, wp/v2) use a different error format (code/message/data).

This PR got a bit complex, but the main idea is that each type of request can define a validator that might convert a response into an error. This is useful because a DotcomRequest might want to do a different thing depending on the wordpressApiVersion.

Testing instructions

The easiest way to force an error is to modify InAppPurchasesRemote and make sure the X-APP-ID header has an unknown identifier (e.g. Bundle.main.bundleIdentifier?.appending(".unknown")).

Then:

1. Go to Hub menu > Debug IAP
2. Wait for the products to load
3. Look at the console for an error

If you test this on trunk, all you would see is a parsing error:

Error loading products: typeMismatch(Swift.Array, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Array but found a dictionary instead.", underlyingError: nil))

With the changes in this PR, you should see a more specific error:

Error loading products: WordPress API Error: [rest_forbidden] Sorry, you are not allowed to do that.

---

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr8031-0ae120c on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[peril-woocommerce]

	Warnings
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

Generated by 🚫 dangerJS

[toupper]

The code looks good to me and it tests well! 🎉 It's nice that we have now more specific error messages:

2022-11-04 12:57:32.026167+0100 WooCommerce[12468:3206818] <> Mapping Error: WordPress API Error: [rest_forbidden] Sorry, you are not allowed to do that.
2022-11-04 12:57:32.026460+0100 WooCommerce[12468:3206819] [💰IAP Store] Failed obtaining product list from StoreKit: WordPress API Error: [rest_forbidden] Sorry, you are not allowed to do that.
Error loading products: WordPress API Error: [rest_forbidden] Sorry, you are not allowed to do that.

I got three repeated error messages, but I guess it's because we log them at every level of our IAP architecture.

[toupper]

We already have an enum for WordPress.com Request Errors (DotcomError), for me to understand, do these two enums have different purposes?

[koke]

This is for the core API errors, which might come from WordPress.com (wpcom/v2, wp/v2) or directly from a self-hosted site (via WordPressOrgRequest). There might be some overlap, but error codes might not necessarily match.

[koke]

I got three repeated error messages

Oh good catch. I think the "Mapping error" shouldn't be there. Previously it would only log if the error was coming from the mapper, but since I consolidated the error handling, it's too verbose now.