Issue:
refactor(connector): [bluesnap] add connector_txn_id fallback for webhook

## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [ ] Enhancement
- [X] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
add connector_txn_id fallback for webhook

### 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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1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
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If it fixes an open issue, please link to the issue here.

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#3316 

## How did you test it?
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Trigger webhooks from Bluesnap with and without `merchant_transaction_id` and receive outgoing webhooks from Hyperswitch

<img width="1424" alt="Screenshot 2024-01-10 at 7 13 24 PM" src="https://github.com/juspay/hyperswitch/assets/55536657/5a743336-f53a-421f-9d23-d0e75344232d">




## 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


Resolution:
<think>
PR Context:
- Title: refactor(connector): [bluesnap] add connector_txn_id fallback for webhook
- Merged: 2024-01-10T14:54:49Z
- Files changed: 1 files
- Commits: 2 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [ ] Enhancement
- [X] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
add connector_txn_id fallback for webhook

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

<!--
Provide
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** refactor(connector): [bluesnap] add connector_txn_id fallback for webhook (#3317)
Files to modify:


**crates/router/src/connector/bluesnap.rs**
  Modify existing code