Issue:
Updating the API reference documentation - payments

We have had feedback related to the API doc being outdated, and lacking proper visibility of the latest spec of the API collection.

Resolution:
<think>
PR Context:
- Title: Docs: Updated API - ref for payments
- Merged: 2024-07-04T13:33:48Z
- Files changed: 4 files
- Commits: 13 commits

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

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** Docs: Updated API - ref for payments (#5172)
Co-authored-by: hyperswitch-bot[bot] <148525504+hypersw
Files to modify:


**crates/api_models/src/payments.rs**
  Modify existing code

**crates/common_enums/src/enums.rs**
  Modify existing code

**crates/openapi/src/routes/payments.rs**
  Modify existing code