fix: tiles object manager

[pauldambra]

Problem

Since extending soft delete to dashboard tiles we've had to remember to exclude deleted tiles (which is easy to forget e.g. #13629)

It's also easy to cause N+1 by excluding or not when the ORM isn't expecting it

was stacked on top of #13629

Changes

• overrides the ModelManager on Insight, Dashboard, and DashboardTile to always exclude soft-deleted models
• adds a model manager to each to allow access to a queryset including soft-deleted items
• removes an N+1 we had to add in fix: deleted tile aware insights #13599

How did you test this code?

running the tests, checking locally

[Twixes]

This is way more obvious, with the small exception of including_soft_deleted 😅

[Twixes]

Hmm, definitely not typical to have two managers on a model. Lots of redundancy. Can we maybe instead add a method like all_even_soft_deleted() to DashboardTileManager()? That'd be plain super().get_queryset()

[pauldambra]

Hmmm 🤔 I pretty much lifted this straight out of the docs https://docs.djangoproject.com/en/4.1/topics/db/managers/#modifying-a-manager-s-initial-queryset

How about rename to objects_including_soft_deleted? That way as someone starts to type objects... intellisense will show them there are two options?

[Twixes]

Oh fair enough, looks like I skipped out on that part of the docs :D

[pauldambra]

You've not memorised the entire Django docs 🤯 🤣

[Twixes]

You bet I've used summaries for the boring required reading books in school