fix(address): use first_name if last_name is not passed

[Narayanbhat166]

Type of Change

• Bugfix

Description

This PR fixes the issue which arises when creating a payement with cybersource and bank of america connectors where billing first name and last name are mandatory.

Motivation and Context

How did you test it?

• Create a payment by passing billing address in payment create request, with confirm set to false.

curl --location 'http://localhost:8080/payments' \
--header 'Content-Type: application/json' \
--header 'api-key: dev_uHrHd27n2djqmWLoWqhpHPf1NmU2dsIbEguhDIB9ji7bQmzf9rLqw9TqrsRybqwm' \
--data-raw '{
    "amount": 6540,
    "currency": "USD",
    "confirm": false,
    "customer": {
        "id": "cus_abc",
        "email": "example@juspay.in"
    },
    "billing": {
        "address": {
            "line1": "1467",
            "line2": "Harrison Street",
            "city": "San Fransico",
            "state": "California",
            "zip": "94122",
            "country": "US",
            "first_name": "Narayan",
            "last_name": "Bhat"
        }
    }
}'

• Confirm the payment with card_holder_name, by not passing last name

curl --location 'http://localhost:8080/payments/pay_QHybdDJQVMZVgS4BX4IQ/confirm' \
--header 'Content-Type: application/json' \
--header 'Accept: application/json' \
--header 'api-key: dev_uHrHd27n2djqmWLoWqhpHPf1NmU2dsIbEguhDIB9ji7bQmzf9rLqw9TqrsRybqwm' \
--data '{
    "payment_method_data": {
        "card": {
            "card_number": "4242424242424242",
            "card_exp_month": "10",
            "card_exp_year": "25",
            "card_holder_name": "Narayan",
            "card_cvc": "123"
        }
    },
    "payment_method": "card"
}'

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code