Better Handling of HTTPResponseError with json + Tests

[designatednerd]

This PR addresses #742 (which is a re-file of #477), and makes sure that when an HTTPResponseError is received, errors are properly parsed.

I also added some tests on this as a net for the future.

[designatednerd]

@jordanhbuiltbyhq Mind taking a look at this to make sure this is the behavior you were looking for?

[jordanhbuiltbyhq]

This is lovely, thanks! Any expectation for when this would go live?

[designatednerd]

I'll take a look and see if anything else needs to be patched but otherwise within the next day or two

[jordanhbuiltbyhq]

Oh I wanted to check, is there a better way to detect an unauthenticated error? Currently I have this not-so-pretty chunk of code:

        if let graphQLError = error as? GraphQLHTTPResponseError {
            if let bodyData = graphQLError.body {
                if let jsonObject = try? JSONSerialization.jsonObject(with: bodyData, options: []) as? [String: Any] {
                    if let errors = jsonObject["errors"] as? [[String: Any]] {
                        if let extensions = errors.first?["extensions"] as? [String: Any] {
                            if let code = extensions["code"] as? String {
                                if code == "UNAUTHENTICATED" {
                                    //TODO: Go to login screen
                                }
                            }
                        }
                    }
                }
            }
        }

[designatednerd]

Woo, pyramid of doom! Takes me back to the early days of Swift 😃

So a couple suggestions: First, use guard let in order to stack your unwraps instead of pyramiding them (you'll see what I mean in the example below). Once this feature lands, you should be able to do something like:

guard 
    let responseError = error as? GraphQLHTTPResponseError,
    let graphQLError = responseError.graphQLErrors?.first, 
    let extensions = graphQLError.extensions,
    let code = extensions["code"] else {
       // No error code to deal with 
      return
}

switch (code) {
case "UNAUTHENTICATED": 
    // Kick to login screen
default: 
   // Whatever else you need to do
}

[designatednerd]

OK gonna merge this, it'll go out in the next patch release - I'll ping your other issue once it ships.