Comment 10 for bug 1940549

At the engineering sprint, it came to my attention that leader-set should be deprecated and "application databag" should be used instead, so this'll need a rework.

Also worth to mention that both Application and Leader databags persist through scaling to zero and then up again. This is an edge case, but we should make sure that the cache gets erased when last unit leaves because new vault instance will probably initiate new CA.