Add an admin action that [calculates the compute and storage costs based on actual challenge usage](https://github.com/DIAGNijmegen/rse-grand-challenge-admin/pull/779) and updates the post-paid invoice with the proper amounts. The admin action should only work for post-paid invoices in initialized state.
Add an admin action that calculates the compute and storage costs based on actual challenge usage and updates the post-paid invoice with the proper amounts.
The admin action should only work for post-paid invoices in initialized state.