No default value for sample.vfn in TrainImagesClassifier

Description

There is no default value for the sample.vfn parameter in otbcli_TrainImagesClassifier.

 -sample.vfn       <string>    Field containing the class integer label for supervision  (mandatory, default value is )

I did try to look where it came from, but I lost myself in all the classes. Maybe its best if the author could take a look. (Ok I admit this is an excuse to test the issue feature of github 👏 )

Steps to reproduce

Run otbcli_TrainImagesClassifier without argument. Reproducibility: always.

Configuration information

Any