This reverts commit 6d416c9a.
Causality on invoice is calculated from movement causality values

Check generation of invoice and payment.

Price grouping should use rounding

It allows to group all invoice line related to the same resource

Some software instances has no open sale order line related.

It will allow to index not instantiated Software Instances.

It is required to try harder to find root hosting subscription, especially
during upgrades.

Users are locked until they will registration payment, as soon as related
invoice is stopped.