Feature Suggestion: Add "expand" Parameter to refund method

[Anemoiaa]

We propose adding an "expand" parameter to the refund method. This improvement, would allow users to specify additional resources to include in the response, reducing the number of requests needed to update information after a transaction refund.

Example Usage $newTransaction = $coreService->transactions()->refund(id: 1, expand: 'invoices,parentTransaction');