Per-user reblog hiding implementation/fixes/tests

Note that this will only hide/show *future* reblogs by a user, and does
nothing to remove/add reblogs that are already in the timeline. I don't
think that's a particularly confusing behavior, and it's a lot easier
to implement (similar to mutes, I believe).

app/models/follow_request.rb

@@ -22,7 +22,7 @@ class FollowRequest < ApplicationRecord
   validates :account_id, uniqueness: { scope: :target_account_id }
 
   def authorize!
-    account.follow!(target_account, reblogs: reblogs)
+    account.follow!(target_account, reblogs: show_reblogs)
     MergeWorker.perform_async(target_account.id, account.id)
 
     destroy!