5.19.0

• Add MerchantTokenIdentifier, SourceCardLast4 to ApplePayCard and ApplePayDetails
• Add ThreeDSecureAuthenticationId to CustomerRequest and PaymentMethodRequest
• Add processing_overrides to Transaction.sale options
• Add industry data fields to TransactionRequest
  • ArrivalDate
  • TicketIssuerAddress
• Remove byte[] to String content conversion for requests containing files in BraintreeService