Cached content should be removed from stream caches when necessary
A concrete example:
- User shares a post from another user
- The post is cached (via the share) into the "all content" stream of the user
- User decides it wasn't worth sharing, and thus unshares it
What should happen: The post is uncached from the "all content" stream IF it has no other reasons to be there (in this case there would be none, since it's a profile stream)
What happens: Post shows in the profile stream but with the sharer empty, as the share was deleted.
This problem exists for all stream caches. For example when unfollowing someone, the posts of that person will still remain in the followed stream even if new posts wont be added there. Ideally the caches would be updated.