Cancel error handling

[KunJeongPark]

Summary of changes

• Provide helper methods to merchants to distinguish cancellation errors from 3DS in cards, PayPal Checkout and vault flows.
• Our SDK is right now returning CoreSDKError to the users. To discern cancellation errors, users need to check domain and code, which are specified by enum values only at internal level, which is cumbersome.
• For next beta release, we should consider restructuring errors returned to merchants so they can easily check for types of errors.
• Demo app changes and unit tests for helper methods
• Cast errors from urlSessions as NetworkingClientError
• Modify completion handlers to return CoreSDKError instead of general error

Without helper methods, merchant has to look up our internal Client level Codes and domain to get matching number, string

if let error {
   if error.code.rawValue == 6 && error.domain == "PayPalClientErrorDomain" {
      // handle cancel error
  } else {
    // handle all other errors
  }
}

With helper method:

if let error {
   if PayPalError.isCheckoutCanceled(error) {
     // handle cancel error
   } else {
    // handle all other errors
   }

Checklist

• Added a changelog entry

Authors

List GitHub usernames for everyone who contributed to this pull request.

• @KunJeongPark