- Introduced `testPaymentMethods` endpoint in InvoicesController to directly test WHMCS payment methods for a specific client ID.
- Added `testWhmcsPaymentMethods` method in InvoicesService for detailed logging and error handling during WHMCS API calls.
- Implemented cache bypassing and enhanced logging in `getPaymentMethods` method of WhmcsPaymentService for debugging purposes.
- Updated payment method transformation logic in WhmcsDataTransformer to handle variations in WHMCS API responses.
- Added debug information in Checkout and AddressConfirmation components to assist in troubleshooting address confirmation flow.
- Introduced `validateSignup` endpoint in AuthController for customer number validation during signup.
- Added `healthCheck` method in AuthService to verify service integrations and database connectivity.
- Implemented `getPaymentMethods`, `getPaymentGateways`, and `refreshPaymentMethods` endpoints in InvoicesController for managing user payment options.
- Enhanced InvoicesService with methods to invalidate payment methods cache and improved error handling.
- Updated currency handling across various services and components to reflect JPY as the default currency.
- Added new dependencies in package.json for ESLint configuration.
