Issue:
[FEATURE] add domain type for client secret 

### Feature Description

Create domain type for client secret

### Possible Implementation

Make type `ClietSecret(String)` and use it wherever applicable

### Have you spent some time to check if this feature request 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?

No, but I'm happy to collaborate on a PR with someone else

Resolution:
<think>
PR Context:
- Title: feat(api_models): add client_secret type to payments
- Merged: 2024-02-15T06:49:24Z
- Files changed: 1 files
- Commits: 6 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [x] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description

Implement `ClientSecret` type for payments. 

Closes #1357 

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables


## Motivation and Context



</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** feat(api_models): add client_secret type to payments (#3557)
Co-authored-by: Sanchith Hegde <2221750
Files to modify:


**crates/api_models/src/payments.rs**
  Add:
    - function: private::deserialize
    - function: private::expecting
    - function: private::visit_str
    - function: private::serialize
    - function: private::test_serialize_client_secret
    - function: private::test_deserialize_client_secret
    - struct: pub::ClientSecret
    - struct: private::ClientSecretVisitor
    - impl: impl Deserialize<'de> for ClientSecret
    - impl: impl Visitor<'de> for ClientSecretVisitor
    - impl: impl Serialize for ClientSecret
    - mod: private::client_secret_tests