INVENTORY ASYNC QUERY
Captures the entire state of the current user's Steam inventory.
You must call DestroyResult on this handle when you are done with it.
Returns false and sets *pResultHandle to zero if inventory is unavailable.
Note: calls to this function are subject to rate limits and may return
cached results if called too frequently. It is suggested that you call
this function only when you are about to display the user's full inventory,
or if you expect that the inventory may have changed.