Add Utility Bill Payments support to Java SDK #23

Hi team,

I’d like to propose adding support for the Utility Bill Payments API to the Java SDK.

From reviewing the existing SDK structure (e.g., GiftcardAPI and its corresponding Operations classes), I plan to follow the same design pattern for consistency.

Proposed Structure

Main API Class:

• UtilityBillAPI (extending ServiceAPI)

Operations Classes:

• UtilityBillAccountOperations

  • getBalance()

• UtilityBillBillerOperations

  • list()

• UtilityBillPaymentOperations

  • pay(PaymentRequest request)

• UtilityBillTransactionOperations

  • list()
  • getById(String id)

Implementation Notes

• Reuse the existing authentication flow (AuthenticationAPI)
• Follow the same request/response pattern using Request<T> and .execute()
• Align with naming conventions and structure used in the gift-card module
• Use existing utilities such as Asserter, TypeReference, and base operation classes

I’ll also include DTOs, examples, and documentation to match the current SDK standards.

Please let me know if this aligns with your roadmap or if you’d prefer any adjustments before I proceed with the implementation.

Thanks!