## Context

This PR extends the invoice voiding logic to support optional credit
note generation, with refund and credit amounts.

Originally, a `confirm_void` parameter was proposed to make the override
explicit. After internal discussion, we decided to simplify the API: the
presence of `generate_credit_note` is now considered an explicit intent
to force the void.

This change preserves backwards compatibility while unlocking more
powerful workflows.

## Description

This pr adds support for the following parameters in the void_invoice
mutation and endpoint:

``` json
{
  "generate_credit_note": true,
  "refund_amount": 2000,
  "credit_amount": 1150
}
```
If no parameters are passed → invoice must be voidable (as before).
If generate_credit_note parameter is passed → invoice is voided ( all
types of invoices can now be voided )

**Partial Credit Note + Remaining Voided Credit**

When a credit note is generated with a refund_amount and/or
credit_amount that does not cover the full invoice amount, the system
will:

1. Generate a first credit note with the specified refund_amount and
credit_amount.
2. Automatically generate a second credit note for the remaining amount,
which is immediately voided.

This ensures that:

- The entire invoice amount is covered across the two credit notes.
- Only the explicitly requested amounts are usable (refunded or
credited).
- The remaining amount is voided and not usable by the customer, but
still bookkept for completeness and compliance.

Example

Invoice total: €20 (2000 cents)
Request:

```  json
{
  "generate_credit_note": true,
  "refund_amount": 1000,
  "credit_amount": 500
}
```

The system will create:
✅ Credit Note 1: €10 refunded + €5 credited (usable)
🚫 Credit Note 2: €5 voided (not usable)

---------

Co-authored-by: Diego Charles <diegocharles@me.com>