feat(router): Support `card` in `payment_method_subtype` [V2]

`payment_method_subtype` field needs to be made mandatory and `card` needs to be added as a supported enum variant.

This is needed for parity with industry standard analytics hierarchy
<think>
PR Context:
- Title: feat(router): Support `card` in `payment_method_subtype` [V2]
- Merged: 2025-04-08T10:20:11Z
- Files changed: 30 files
- Commits: 8 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 -->
- Made `payment_method_subtype` mandatory in API endpoints and `payment_attempt` table
- Added `card` as an enum variant to `payment_method_subtype`

### Additional Changes

- [x] This PR modifies the API contract
- [x] This PR modifies 
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** feat(router): Support `card` in `payment_method_subtype` [V2] (#7662)
Files to modify:


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

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

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

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

**crates/diesel_models/src/payment_attempt.rs**
  Modify existing code

**crates/diesel_models/src/schema_v2.rs**
  Modify existing code

**crates/diesel_models/src/types.rs**
  Modify existing code

**crates/euclid/src/frontend/dir/enums.rs**
  Modify existing code

**crates/euclid/src/frontend/dir/lowering.rs**
  Modify existing code

**crates/euclid/src/frontend/dir/transformers.rs**
  Modify existing code

**crates/hyperswitch_connectors/src/connectors/adyen.rs**
  Modify existing code

**crates/hyperswitch_connectors/src/connectors/chargebee/transformers.rs**
  Modify existing code

**crates/hyperswitch_connectors/src/connectors/klarna.rs**
  Modify existing code

**crates/hyperswitch_connectors/src/connectors/paypal/transformers.rs**
  Modify existing code

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

**crates/hyperswitch_domain_models/src/payments/payment_attempt.rs**
  Modify existing code

**crates/hyperswitch_domain_models/src/revenue_recovery.rs**
  Modify existing code

**crates/kgraph_utils/src/mca.rs**
  Modify existing code

**crates/kgraph_utils/src/transformers.rs**
  Modify existing code

**crates/router/src/connector/stripe/transformers.rs**
  Modify existing code

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

**crates/router/src/core/payments/routing.rs**
  Modify existing code

**crates/router/src/core/payments/transformers.rs**
  Modify existing code

**crates/router/src/core/revenue_recovery/types.rs**
  Modify existing code

**crates/router/src/types/api/payment_methods.rs**
  Modify existing code

**crates/router/src/types/transformers.rs**
  Modify existing code
{"issue_number": 7661, "pr_number": 7662, "commits_count": 1, "files_changed": 30, "response_length": 2814, "file_count": 28, "needs_breakdown": true}