feat(payment_methods): enhance customer payment methods retrieval with modular service support

[GauravRawat369]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

This pull request introduces support for routing customer payment method listing requests through a modular service, based on organizational eligibility. The changes add new request and response types, update query parameter handling, and implement conditional logic to determine whether to use the modular service or the legacy flow. Additionally, a new helper function is provided to facilitate modular service calls with appropriate headers.

Modular service integration for customer payment method listing:

• Added new request (ListCustomerPaymentMethodsV1Request) and response (ListCustomerPaymentMethodsV1Response) types to support modular service calls, including fields for service prefix and guest customer status.
• Updated query parameter construction to handle optional parameters and include the modular service prefix in API paths. [1] [2] [3]

Conditional routing based on organizational eligibility:

• Integrated get_organization_eligibility_config_for_pm_modular_service to determine if requests should be routed to the modular service, and updated the main listing logic to branch accordingly. [1] [2] [3]

Helper function for modular service calls:

• Added list_customer_pml_modular_service_call to build requests, set headers, and invoke the modular service client for payment method listing.

Imports and code organization:

• Updated imports to support new functionality and helper functions for modular service integration. [1] [2]

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

Request

curl --location 'http://localhost:8080/customers/12345_cus_019c2328ac127c018b64028fb83b2537/payment_methods' \
--header 'Accept: application/json' \
--header 'api-key: dev_lYlSW9umndQrewmQ4WYPIjNTZzag4bQZtvNKSCfPkULSCGTgJEdAwyrh5uGQEDFs'

Response

{
    "customer_payment_methods": [
        {
            "payment_token": "12345_pm_019c232911937750a630379930170ab7",
            "payment_method_id": "12345_pm_019c232911937750a630379930170ab7",
            "customer_id": "12345_cus_019c2328ac127c018b64028fb83b2537",
            "payment_method": "card",
            "payment_method_type": "credit",
            "payment_method_issuer": null,
            "payment_method_issuer_code": null,
            "recurring_enabled": true,
            "installment_payment_enabled": null,
            "payment_experience": null,
            "card": {
                "scheme": null,
                "issuer_country": null,
                "issuer_country_code": null,
                "last4_digits": "4242",
                "expiry_month": "03",
                "expiry_year": "2028",
                "card_token": null,
                "card_holder_name": "joseph Doe",
                "card_fingerprint": null,
                "nick_name": null,
                "card_network": null,
                "card_isin": null,
                "card_issuer": null,
                "card_type": null,
                "saved_to_locker": true
            },
            "metadata": null,
            "created": "2026-02-03T11:00:19.987Z",
            "bank": null,
            "surcharge_details": null,
            "requires_cvv": true,
            "last_used_at": "2026-02-03T11:00:19.987Z",
            "default_payment_method_set": false,
            "billing": null
        }
    ],
    "is_guest_customer": null
}

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible

[semanticdiff-com]

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Changed Files

File	Status
crates/payment_methods/src/client/list.rs	82% smaller
crates/router/src/core/payment_methods/cards.rs	47% smaller
crates/router/src/core/payment_methods/transformers.rs	3% smaller