feat(router): [V2] Return connector customer reference IDs in CustomerResponse

[AnuthaDev]

Type of Change

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

Description

Add a field connector_customer to CustomerResponse that contains a map between MerchantConnectorAccountId and connector customer id

Additional Changes

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

Motivation and Context

From #7246:

with respect to the multi-use tokens that were created with Stripe (support added in #7106), the payment methods were created on Stripe's end, but were not associated with a customer, due to which they could not be used to make transactions again, we used to receive such an error:

The provided PaymentMethod cannot be attached. To reuse a PaymentMethod, you must attach it to a Customer first.

To address this, we have to create a customer on Stripe's end first, and then pass Stripe's customer ID when saving the payment method with Stripe.

How did you test it?

• Request:

curl --location 'http://localhost:8080/v2/customers/12345_cus_01951dbc16d57d03ac193a7e297d4899' \
--header 'x-profile-id: pro_Vb32qOaqvkJClXH7aNWK' \
--header 'Authorization: api-key=dev_f4mNrhkUeCtLcsqUaG1fpzHpqTCnPdJMBSPNZAP2nWwwr7FRYtbj1RUdWBPKBKZ0' \
--header 'api-key: dev_f4mNrhkUeCtLcsqUaG1fpzHpqTCnPdJMBSPNZAP2nWwwr7FRYtbj1RUdWBPKBKZ0'

• Response:

{
    "id": "12345_cus_01951dbc16d57d03ac193a7e297d4899",
    "merchant_reference_id": "customer_1739960621",
    "connector_customer": {
        "mca_hwySG2NtpzX0qr7toOy8": "cus_Rnm2pDKGyQi506"
    },
    "name": "John Doe",
    "email": "guest@example.com",
    "phone": "999999999",
    "phone_country_code": "+65",
    "description": "First customer",
    "default_billing_address": null,
    "default_shipping_address": null,
    "created_at": "2025-02-19T10:23:40.758Z",
    "metadata": {
        "udf1": "value1",
        "new_customer": "true",
        "login_date": "2019-09-10T10:11:12Z"
    },
    "default_payment_method_id": 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
api-reference-v2/openapi_spec.json	0% smaller
crates/api_models/src/customers.rs	0% smaller
crates/common_types/src/customers.rs	0% smaller
crates/common_types/src/lib.rs	0% smaller
crates/diesel_models/src/customers.rs	0% smaller
crates/hyperswitch_domain_models/src/customer.rs	0% smaller
crates/router/src/types/api/customers.rs	0% smaller