Feature request: PPANMETH column to detail interval operations

[Gero1999]

PKNCA details about calculation methods are not completely obvious by just looking at the results. One potential fix would be to add this PPANMETH column, which is a recognised SDTM column to detail specific analysis methods used in the calculation of a parameter. We could use it so far for:

• For AUC-based parameters, indicate AUC method of calculation (“lin up/log down”, “linear”, “lin-log”)
• For intervals with impute column actions, the specific imputation performed
• If any global imputation for BLQ or NA action was done, indicate it also in this column.
• When implemented, indicate the reference in parameter-ratio operations
• For lambda Z direct parameters, would be good to indicate if there was any manual inclusion/exclusion!

This will make more transparent and differentiate better PKNCA results