Invoices: stage replaces approvalStatus (experimental)

Invoices and credit notes now carry a stage: where they are in their lifecycle, from approval to payment. It is returned by List invoices and Get invoice, and all three invoice endpoints, the summary included, accept a stage filter.

`stage`	Meaning
`pendingApproval`	Awaiting a decision in the approval workflow
`inReview`	Approved, waiting for the controller review
`disputed`	Approved, then put in dispute with the supplier (invoices only)
`toSettle`	Reviewed: an invoice waiting for payment, fully or in part; a credit note partially allocated
`settled`	An invoice fully paid; a credit note fully allocated or reimbursed
`rejected`	Declined by an approver, rejected in controller review, or expired
`cancelled`	Withdrawn by the company

Without a stage filter, every stage except cancelled is returned.

🚧
Breaking change: approvalStatus is removed
approvalStatus is no longer returned on invoices, and no longer exists as a filter. Read stage instead, and replace the filter:

approvalStatus=pending → stage=pendingApproval;

approvalStatus=approved → stage=inReview&stage=toSettle for approved invoices still to pay; add disputed and settled for every approved invoice;

approvalStatus=rejected → stage=rejected.

A request that still sends approvalStatus is not refused: the filter is ignored, so the list comes back unfiltered.

curl --request GET \
     --url 'https://public-api.spendesk.com/v2/companies/7j6mvn11rqf7j5/invoices?stage=inReview&stage=toSettle&limit=50' \
     --header 'accept: application/json' \
     --header 'authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.masked'

The recipes List the invoices due this week and Month-end close checklist use the new filter. These endpoints remain experimental (scope experimental:invoice:read).

Breaking change: approvalStatus is removed

Breaking change: `approvalStatus` is removed