feat(payment_methods): Use Ephemeral auth for pm list and pm delete

[Sarthak1799]

Type of Change

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

Description

This PR enables -

• Ephemeral key auth for customer's pm list
• Ephemeral key auth for delete payment method

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?

1. Save a card for a customer
2. Create Ephemeral key for that customer

curl --location --request POST 'http://localhost:8080/ephemeral_keys' \
--header 'Content-Type: application/json' \
--header 'api-key: dev_cHN6hMdCFUUrNWjYSxnwhiuMsg83rXTX9jBmtHmCL6sq9a43PswY304MSt3a9blR' \
--data-raw '{
    "customer_id": "cus_q1KVr57JhvRlVHToTKkY"
}'

Response -

{
    "id": "eki_DuTISISBl1O0MAyczMQ8",
    "merchant_id": "sarthak1",
    "customer_id": "cus_grCxh6TyR6uepXyc6p7q",
    "created_at": 1718270809,
    "expires": 1718274409,
    "secret": "epk_67d4e3b46c49402badcbff4901cfef67"
}

3. Use the Ephemeral key secret to call customer's pm list

curl --location --request GET 'http://localhost:8080/customers/payment_methods' \
--header 'Accept: application/json' \
--header 'api-key: epk_be243219006647c69cdd7111d490d79a'

Response -

{
    "customer_payment_methods": [
        {
            "payment_token": "token_9OtU08A46TOZcmfislqy",
            "payment_method_id": "pm_RPkRCYXKIWZFj0Qr36E9",
            "customer_id": "Some_cust1",
            "payment_method": "card",
            "payment_method_type": null,
            "payment_method_issuer": null,
            "payment_method_issuer_code": null,
            "recurring_enabled": false,
            "installment_payment_enabled": false,
            "payment_experience": [
                "redirect_to_url"
            ],
            "card": {
                "scheme": null,
                "issuer_country": null,
                "last4_digits": "4242",
                "expiry_month": "10",
                "expiry_year": "2025",
                "card_token": null,
                "card_holder_name": "joseph Doe",
                "card_fingerprint": null,
                "nick_name": null,
                "card_network": null,
                "card_isin": "424242",
                "card_issuer": null,
                "card_type": null,
                "saved_to_locker": true
            },
            "metadata": null,
            "created": "2024-06-13T09:59:16.717Z",
            "bank": null,
            "surcharge_details": null,
            "requires_cvv": true,
            "last_used_at": "2024-06-13T09:59:16.717Z",
            "default_payment_method_set": true,
            "billing": {
                "address": {
                    "city": "San Fransico",
                    "country": "US",
                    "line1": "1467",
                    "line2": "Harrison Street",
                    "line3": "Harrison Street",
                    "zip": "94122",
                    "state": "California",
                    "first_name": "john",
                    "last_name": "Doe"
                },
                "phone": {
                    "number": "8056594427",
                    "country_code": "+91"
                },
                "email": null
            }
        }
    ],
    "is_guest_customer": null
}

4. Separate flow, Delete a PM using Ephemeral key

curl --location --request DELETE 'http://localhost:8080/payment_methods/pm_RPkRCYXKIWZFj0Qr36E9' \
--header 'Accept: application/json' \
--header 'api-key: epk_be243219006647c69cdd7111d490d79a'

Response -

{
    "payment_method_id": "pm_RPkRCYXKIWZFj0Qr36E9",
    "deleted": true
}

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

[racnan]

Authentication can be done in a neater way.

[racnan]

this can be done in authenticationAndFetch function.
we should refrain from passing keys in core functions.