Issue:
Bug: [FEATURE] : [Klarna] mask pii information in connector request and response



### Feature Description

Mask pii information passed and received in the connector request and response

### Possible Implementation

Refactor all sensitive response and request fields secret

### Have you spent some time checking if this feature request has been raised before?

- [X] I checked and didn't find a similar issue

### Have you read the Contributing Guidelines?

- [X] I have read the [Contributing Guidelines](https://github.com/juspay/hyperswitch/blob/main/docs/CONTRIBUTING.md)

### Are you willing to submit a PR?

Yes, I am willing to submit a PR!

Pull request description:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [x] Enhancement
- [x] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
Mask pii information passed and received in the connector request and response for Klarna.


## Test Cases
<!--
Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
-->
1. Create a Klarna payment with Klarna connector. Set payment experience as invoke SDK.
_Note: As it requires invoking SDK, can't be tested from local_


## Checklist
<!-- Put an `x` in the boxes that apply -->

- [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:

Patch:
diff --git a/crates/router/src/connector/klarna/transformers.rs b/crates/router/src/connector/klarna/transformers.rs
index c12f8ed1b10..29dccfbf32b 100644
--- a/crates/router/src/connector/klarna/transformers.rs
+++ b/crates/router/src/connector/klarna/transformers.rs
@@ -1,6 +1,6 @@
 use api_models::payments;
 use error_stack::report;
-use masking::Secret;
+use masking::{ExposeInterface, Secret};
 use serde::{Deserialize, Serialize};
 
 use crate::{
@@ -66,8 +66,8 @@ pub struct KlarnaSessionRequest {
 
 #[derive(Deserialize, Serialize, Debug)]
 pub struct KlarnaSessionResponse {
-    pub client_token: String,
-    pub session_id: String,
+    pub client_token: Secret<String>,
+    pub session_id: Secret<String>,
 }
 
 impl TryFrom<&types::PaymentsSessionRouterData> for KlarnaSessionRequest {
@@ -110,8 +110,8 @@ impl TryFrom<types::PaymentsSessionResponseRouterData<KlarnaSessionResponse>>
             response: Ok(types::PaymentsResponseData::SessionResponse {
                 session_token: types::api::SessionToken::Klarna(Box::new(
                     payments::KlarnaSessionTokenResponse {
-                        session_token: response.client_token.clone(),
-                        session_id: response.session_id.clone(),
+                        session_token: response.client_token.clone().expose(),
+                        session_id: response.session_id.clone().expose(),
                     },
                 )),
             }),