confirm-intent API contract changes for split payments (v2)

In v2, we need to support receiving multiple payment methods in the confirm-intent request. Add a new field to support this use case
<think>
PR Context:
- Title: feat(router): Add Confirm-Intent API contract changes for split payments (v2)
- Merged: 2025-09-25T17:56:40Z
- Files changed: 3 files
- Commits: 3 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [x] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
- Added `split_payment_method_data` field to `confirm-intent` call to accept a `Vec` of payment methods

<img width="502" height="763" alt="image" src="https://github.com/user-attachments/assets/69ae3cc4-3d06-4980-b2d9-52b489aa98ad" />

##
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** feat(router): Add Confirm-Intent API contract changes for split payments (v2) (#9469)
Files to modify:


**crates/api_models/src/payments.rs**
  Add:
    - struct: pub::SplitPaymentMethodDataRequest

**crates/openapi/src/openapi_v2.rs**
  Modify existing code
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