[REFACTOR] facilitapay destination bank account number should be merchant facing

destination bank account number should be added by merchant, not customer. this is a design flaw that needs to be fixed.
<think>
PR Context:
- Title: refactor(connector): [facilitapay] move destination bank account number to connector metadata
- Merged: 2025-07-25T12:44:09Z
- Files changed: 11 files
- Commits: 7 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 -->

Destination bank account id should be merchant facing, not customer. This PR removes any references to destination bank account id and moves it to connector metadata instead.

### Additional Changes

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

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** refactor(connector): [facilitapay] move destination bank account number to connector metadata (#8704
Files to modify:


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

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

**crates/hyperswitch_connectors/src/connectors/facilitapay/transformers.rs**
  Remove:
    - function: private::from_auth_type
    - function: private::try_from
    - function: private::try_from
    - struct: pub::FacilitapayAuthType
    - impl: impl FacilitapayAuthRequest
    - impl: impl TryFrom<&ConnectorAuthType> for FacilitapayAuthType
    - impl: impl TryFrom<&RefreshTokenRouterData> for FacilitapayAuthRequest
  Add:
    - function: private::from_auth_type
    - function: private::try_from
    - function: private::try_from
    - function: private::try_from
    - struct: pub::FacilitapayAuthType
    - struct: pub::FacilitapayConnectorMetadataObject
    - impl: impl FacilitapayAuthRequest
    - impl: impl TryFrom<&ConnectorAuthType> for FacilitapayAuthType
    - impl: impl TryFrom<&RefreshTokenRouterData> for FacilitapayAuthRequest
    - impl: impl TryFrom<&Option<pii::SecretSerdeValue>> for FacilitapayConnectorMetadataObject

**crates/payment_methods/src/configs/payment_connector_required_fields.rs**
  Modify existing code

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