Fix: Use new OneSignalClientError type for callbacks

[nan-li]

Description

One Line Summary

Add a OneSignalClientError type in the HTTP client to pass to failure callbacks with more precise information.

Details

Motivation

• This is to fix [Bug]: After latest fix I got another crash reports on Crashlytics 😔 #1526 and prevent future similar bugs.
• The bugs are related to limitations of Objective-C to provide nullability and type safety
• Using the generic NSError as the error object to callbacks leads to bugs when trying to read elements from the built-in userInfo dictionary, which can contain anything.
• This reported crash happened as we read an element from that dictionary expecting the return value to be a dictionary. While true most of the time, it was sometimes an NSError instance instead, when JSON parsing of the HTTP response fails.
• Now, calls to client to execute request will use this new OneSignalClientError object in the callback instead of NSError.

Scope

• Direct calls to the client will receive OneSignalClientError, which wraps an underlying NSError instance.
• Failure blocks further up the chain will still receive NSError, extracted from the underlying NSError.

Testing

Unit testing

Updated to build, no new ones added

Manual testing

iPhone 13 with iOS 18.1

1. Reproduced reported crash exactly
2. Fixed issue
3. Forced different failure scenarios to test the changes are working

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
• I have reviewed this PR myself, ensuring it meets each checklist item

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