Validation Config File from the Repository

[signedav]

Since this integration #828 we can store config files per project. In UsabILIty Hub we can store the project variable, means the path. When the path is already an ilidata:key then this could work as long as it's stored per model.

At the moment this ilidata:key needs to be entered manually (no file from the repo selectable in the line edit of the validator - not sure if it should be supported, because it would be the only functionality where we use the repos after project generation (during editing)).

But if it's a path to a file this file will not be "exported" into a topic. It's a conceptional thing. Usually we do not store files permanently on a Topping import. So where should this file be stored?

As attachment file next to the project file (but on generation there is not a project file stored - so complicated)

Write it into the project (but this is very intransparent)

Being able to export it and add it as topping-file (like the catalogue file) - after that the key is written to this specific project variable (preferred possibility)