Issue:
[BUG] merchant account delete does not delete the `merchant_key_store`

### Bug Description

When a merchant is created a `merchant_key_store` is created, which goes along with the `merchant_account`. But when the merchant account is deleted, the key store is not deleted. 

### Expected Behavior

Both merchant account and key store should be delted.

### Actual Behavior

The key store still exists. 

### Steps To Reproduce

- Create a merchant account.
- Delete the merchant account.

### Context For The Bug

_No response_

### Environment

Local

### Have you spent some time checking if this bug 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?

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

Resolution:
<think>
PR Context:
- Title: fix(router): merchant account delete does not delete the merchant_key_store
- Merged: 2023-10-03T18:13:00Z
- Files changed: 3 files
- Commits: 8 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
Closes #2154 by calling `delete_merchant_key_store_by_merchant_id` at `merchant_account_delete`

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies applicatio
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** fix(router): merchant account delete does not delete the merchant_key_store (#2367)
Files to modify:


**crates/diesel_models/src/query/merchant_key_store.rs**
  Add:
    - function: pub::delete_by_merchant_id

**crates/router/src/core/admin.rs**
  Modify existing code

**crates/router/src/db/merchant_key_store.rs**
  Add:
    - function: private::delete_merchant_key_store_by_merchant_id
    - function: private::delete_merchant_key_store_by_merchant_id