Array to string conversion CardBrand error

[james-ingold]

Error can occur after a capture response when returning the transaction back to the UI and having to json serialize it. Need to properly handle the availableNetworks array. I don't have a debug id but here is the relevant call stack:

paypal-server-sdk/src/Models/CardResponse.php in PaypalServerSdkLib\Models\CardResponse::jsonSerialize at line 298
paypal-server-sdk/src/Models/CardBrand.php in PaypalServerSdkLib\Models\CardBrand::checkValue at line 115

Patch fix is here

[LeonarthusMectus]

@james-ingold

As per usual, thank you for the report. I think the fix seems quite reasonable and I'm going to see if/when we can get this worked into the SDK generator.