Transport - Get values of shipments by commodity and mode from FAF for domestic and international trade

[WesIngwersen]

Using code in stateior like
https://github.com/USEPA/stateior/blob/e2a230c2beeb7fe76263ed8db2588fa00be11346/R/CommodityFlowFunctions.R#L14-L15
as an example we can load the stored FAF data for a given year

The goal will be to use these data to get values of shipments by commodity and by mode

Years covered should be 2012-2023

Some questions to be answered:

1. Do we use the value_{YEAR} or the current_value_{YEAR} field? stateior code differentiates by year on which value field it uses.
2. Do we use existing mapping to BEA? stateior maps it to BEA here https://github.com/USEPA/stateior/blob/e2a230c2beeb7fe76263ed8db2588fa00be11346/R/CommodityFlowFunctions.R#L71-L75

[WesIngwersen]

Do we use the value_{YEAR} or the current_value_{YEAR} field? stateior code differentiates by year on which value field it uses?

Per [FAF guide](Do we use the value_{YEAR} or the current_value_{YEAR} field? stateior code differentiates by year on which value field it uses.) current_value_{YEAR} is current dollars for the given year. We should use this value.