Issue:
Bug: [FIX] unmask last4 when metadata changed during /payments



When a metadata is changed during /payments and list customer payment method is called, last4 digits is getting masked. Unmask it and respond with raw string.

Pull request description:
## Type of Change
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- [ ] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
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When a metadata is changed during /payments and list customer payment method is called, last4 digits is getting masked. This PR unmasks it

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
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## How did you test it?
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1. Save a card in locker using /payments
2. Change the metadata of the saved card and try to save it again in locker using /payments
3. Now when list_customer_payment_method is called, the last4_digits field of the updated card has to be unmasked

## Checklist
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- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable


Testing:

1. Save a card in locker using /payments
2. Change the metadata of the saved card and try to save it again in locker using /payments
3. Now when list_customer_payment_method is called, the last4_digits field of the updated card has to be unmasked

Patch:
diff --git a/crates/router/src/core/payments/tokenization.rs b/crates/router/src/core/payments/tokenization.rs
index 9691ea962fa..7cff6263344 100644
--- a/crates/router/src/core/payments/tokenization.rs
+++ b/crates/router/src/core/payments/tokenization.rs
@@ -209,9 +209,7 @@ where
                                         let updated_card = Some(CardDetailFromLocker {
                                             scheme: None,
                                             last4_digits: Some(
-                                                card.card_number.to_string().split_off(
-                                                    card.card_number.to_string().len() - 4,
-                                                ),
+                                                card.card_number.clone().get_last4(),
                                             ),
                                             issuer_country: None,
                                             card_number: Some(card.card_number),