Add applepay and googlepay to public enum PaymentSourceType

[Yannie-Chen]

Add applepay and googlepay to public enum PaymentSourceType

Description

Purpose: to allow merchants only display applepay or googlepay if they wish so.
In the API reference, there is a allow_payment_methods field to allow merchants only display applepay or googlepay, but these two are not in the enum PaymentSourceType, therefore merchants are not able to have applepay or googlepay only in src/main/java/com/checkout/payments/hosted/HostedPaymentRequest.java

Proposed Solution

Add applepay and googlepay to public enum PaymentSourceType