Issue:
Bug: [BUG] "reason" field not being updated while hitting the Refunds - Update endpoint



### Bug Description

Upon hitting the `Refunds - Update` endpoint, we receive a 200 OK response but the `reason` field is not being updated.

### Expected Behavior

The `reason` field should be updated as per the specified message.

### Steps To Reproduce

Hit the `Refunds - Update` endpoint and pass a different reason message than the previous one.

### Environment

Local

### Have you spent some time to check if this bug has been raised before?

- [X] I checked and didn't find 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 -->

- [x] Bugfix

## Description
<!-- Describe your changes in detail -->
The `reason` field is incorrectly mapped in the core logic so this PR modifies that. Also, the `refund_reason` field is missing in the db update function so this PR adds that.

## Motivation and Context
<!--
Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.

If you don't have an issue, we'd recommend starting with one first so the PR
can focus on the implementation (unless its an obvious bug or documentation fix
that will have little conversation).
-->
This PR fixes [this](https://github.com/juspay/hyperswitch/issues/1523) issue.

## How did you test it?
<!--
Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
-->
Tested manually using Postman.

## 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 submitted code

Testing:

Tested manually using Postman.

Patch:
diff --git a/crates/diesel_models/src/refund.rs b/crates/diesel_models/src/refund.rs
index b0b1f03f200..595d54ea7f4 100644
--- a/crates/diesel_models/src/refund.rs
+++ b/crates/diesel_models/src/refund.rs
@@ -190,6 +190,7 @@ impl RefundUpdate {
             refund_error_code: pa_update.refund_error_code.or(source.refund_error_code),
             refund_arn: pa_update.refund_arn.or(source.refund_arn),
             metadata: pa_update.metadata.or(source.metadata),
+            refund_reason: pa_update.refund_reason.or(source.refund_reason),
             ..source
         }
     }
diff --git a/crates/router/src/core/refunds.rs b/crates/router/src/core/refunds.rs
index d4ee45dce47..b0dc979b7cb 100644
--- a/crates/router/src/core/refunds.rs
+++ b/crates/router/src/core/refunds.rs
@@ -700,7 +700,7 @@ impl ForeignFrom<storage::Refund> for api::RefundResponse {
             refund_id: refund.refund_id,
             amount: refund.refund_amount,
             currency: refund.currency.to_string(),
-            reason: refund.description,
+            reason: refund.refund_reason,
             status: refund.refund_status.foreign_into(),
             metadata: refund.metadata,
             error_message: refund.refund_error_message,