stockpile

An inventory engine: stock arrives as lots with a receipt date and an

expiry, can be reserved, committed into an order, cancelled back,

transferred between warehouses, and expired out of availability.

Quantities are exact integers; the difficulty is in the rules, not the

arithmetic.

The FEFO allocation module is declared and specified to the unit, but its body

raises NotImplementedError; that is the shape of the feature task built on

this fixture. The rest of the suite is narrow on purpose, so a defect can hide

behind it. Run the suite with pytest.