The idea
Add an option to have the discarded line from the data source saved in a log file when the validation condition isn't satisfy
Use case :
Sometime, you now the row is in error and discard it as to not mess up the entity but it would be preferable to have a simple way to show the error to the end-user to ensure the quality and correctness of the dataset you've just load. Right now you just have a number in the log but no simple way to display the actual row.
In my use case it could be the same file that error but maybe for more flexibility a separated file could be better.
