Show blocked/following status on others' block lists

[jsha]

When viewing someone else's block list it would be nice to have a column for whether you follow or block each of the users. Ideally this should also be sortable. This may be hard to implement. We probably don't want to use the friendships/lookup endpoint since we'd have to call it many times (e.g. 5000 users on a block list = 50 fetches), so we'd have to do it gradually and cache the results. Instead we'd do a join with the viewing user's blocks, for the block aspect. For following we'd also have to fetch, store, and keep updated the viewing user's follow list.

This is relatively low priority, more just an idea.