This means content views like export-library and import-library.

To reproduce:

1) Run hammer content-export complete library or hammer content-export complete repository and see the generated content views
2) Assign a content host to one of those generate content views

Hosts shouldn't be able to be assigned to any of these "behind the scenes" content views.

Important note: there may be users who have already registered their machines to the generated views. It's unclear since it appears that generated views don't get Candlepin environments from (https://projects.theforeman.org/issues/35192).
If we can prove that no clients were able to register to these views, than no migration is needed. If clients could potentially be registered to these views, we'll need some way to migrate them to a normal view (like the actual Default Organization View).