[facturation] Obtain stats on invoicing and proceed to validation.
Add an Invoice model
* Add a PricePerAct model and its management. The price of the acts can change. So a price apply on a period.
* build_invoices_from_acts() is the function that group acts billable in invoices
* get_stats_or_validate() return the stats of an invoicing. It can also be used to validatean invoicing what create Invoice instances, charge healthcare and set acts as billed.
[facturation] Obtain stats on invoicing and proceed to validation.
can change. So a price apply on a period. * build_invoices_from_acts() is the function that group acts billable
in invoices * get_stats_or_validate() return the stats of an invoicing. It can
also be used to validatean invoicing what create Invoice instances,
charge healthcare and set acts as billed.