hub: cleanup data of deleted projects

[haraldschilly]

Description

• on-prem related
• updating pg + @types/pg (because I needed a function, and typing inconsistent)
• generic and robust bulk delete operation
• lot's of problems with actually running tests. I hope my changes fix this for good. Hard to test for me, because locally so many tests fail.
• new destructive actions
  • calling db.delete_syncstring for all strings of deleted projects
  • for onprem only, cleaning up various tables, where rows reference a deleted project

TODO

• central log:
  • check collected data
  • add an entry about each unlinked and deleted project, to have a paper trail

EXTRA

"modernize" visibility and delete controls (popconfirm, switch) … text and so on are the same.

Checklist:

• Testing instructions are provided, if not obvious
• Release instructions are provided, if not obvious

[williamstein]

huge +1! It'll be a good foundation for doing this better in general.

[williamstein]

Think twice about blobs. I would not delete the blobs.

[williamstein]

I'm working on implementing an exam mode for courses. This must involve creating a new project per student for each exam, because it seems it is VERY important to instructors that students don't have access to the exam when the exam is over (and also temporarily don't have access to their own work). This means that the student should be removed from the exam project and their work collected when the exam ends. It would be natural at that point to delete the exam project.
However... it would also be VERY good for the instructor to have access to the TimeTravel data from the exam, which means not deleting the exam project... or at least the edit history in the database.

I understand a big point of this PR is to make it so when you delete a project, all TimeTravel edit history also gets permanently purged. I'm just trying to figure out what to do here...

No comment is needed, probably -- I just wanted to write this down.