Output one or multiple TRK_ITEM based on the number of (sub)-RWBs available for a booking based on the rules below. The sub-RWB number will be assigned to the REF_DOC_NO element in TRK_ITEM.

If booking has:

1. 0 sub-rwb, 1 TRK_ITEM using the default RWB no.
2. 1 sub-rwb, 1 TRK_ITEM using the sub-RWB no.
3. n sub-rwbs, n TRK_ITEMs using the list of sub-RWB numbers, ignoring the default RWB.