Post-process data validation

[aquemy]

For each step, we should check data consistency and format.
For instance, we can check that each section is tagged after preprocessing. All documents that could not be parsed should be returned. At the end of the workflow, it is expected to have one single file with all cases that could not be properly processed, with the step and the reason. This document will serve to adjust and enhance the process, but also to display on the main website for users to know what cases they will not find in the final database.