Also expose payment in sequence.

The sections are not definitive on Payment Transaction, so inventory API will
allow to easily find the payments, by checking balance with given states.

Payment shall represent fact that customer will give money.

This documents allow to lower balance of customer, Payment Transaction shall
not be used.

It is required in order to have them accounted.

LockPerson and UnlockPerson name does not explains that alarm is triggered.

This is done by fixing Person's consistency while Person is added.

Create only one and use tag in order to avoid race conditions.

There are just two states, and unlocked one allows to request Software Instance.

Each person needs to be related with exactly one Open Sale Order.

It shall be related with exactly one Hosting Subscription and when it is in
planned, ordered or confirmed state this Hosting Subscription shall be present
on exactly one Open Sale Order Line.