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/concerns/account_interactions.rb

@@ -81,7 +81,7 @@ module AccountInteractions
       rel.show_reblogs = reblogs
       rel.save!
     end
-    
+
     rel
   end
 
@@ -156,6 +156,10 @@ module AccountInteractions
     mute_relationships.where(target_account: other_account, hide_notifications: true).exists?
   end
 
+  def muting_reblogs?(other_account)
+    active_relationships.where(target_account: other_account, show_reblogs: false).exists?
+  end
+
   def requested?(other_account)
     follow_requests.where(target_account: other_account).exists?
   end