Descriptive errors

[zoejessica]

Three changes to increase the descriptiveness and accuracy of some HotwireNative errors:

• conforms RedirectHandlerError to LocalizedError so we can pass on an exact description of the underlying error to the client
• ensures that we use the precise status code passed from the server when a redirect failed, instead of always assuming a 0 status code.
• fail with a contentTypeMismatch error (instead of status code 0) if the the url response is neither http nor a blob

[svara]

This is a good start. However, I'd like us to consolidate all the errors (maybe in a follow up PR?). Similar to what Android has.

I imagine an enum like:

enum HotwireNativeError: Error {
    case redirectionFailed(reason: RedirectFailureReason)
    ...
}

HotwireNativeError would encompass a few different types of errors, each with their own associated reasons.

[zoejessica]

This is a good start. However, I'd like us to consolidate all the errors (maybe in a follow up PR?). Similar to what Android has.

Yes I agree, and I'll do it in this PR – this was really to get the ball rolling, starting off with the code we're already shipping in production. I'll refine! 👍