Discussion: Use cases of post-import Validators

It would help if we have a list of use-cases that we need to cover with validators, so we can best judge if the current architecture is suitable or not, and how to work towards a better arch. if needed.

Current use-cases would include:
- [ ] - TheSun migration, where they provided a 1st dump with X amount of posts, then a second dump with X-Y amount of posts, and we needed to delete the imported posts that was not included in the second dump.
- [ ] - ?

Start by reviewing the existing validator architecture and the TheSun migration scenario described in the issue. Document the remaining validator use cases and identify what architecture questions they raise; done means the list is complete enough to evaluate the current design.

Written by the indexing model from the issue text.