yes, this will work. You can extend FileDescriptor, add a column to it and assign it at @PostConstruct.
However, there is another (oftentimes a more simple) approach. Use “delegation” instead of inheritance. In this case, you would create a business entity, let’s call it “Attachement” and you’ll make this entity SaaSable with the column e.g. And then you assign a One-To-One association to it to the actual FileDescriptor.
This has to upside that you can easily customize / define the UI for this thing, since you don’t have to extend the default FileDescriptor. Additionally you might want do execute some business logic when a Attachement is created etc.