Cache featured collections, as well as outbox, followers and following (#10467)

app/controllers/activitypub/outboxes_controller.rb

@@ -7,8 +7,14 @@ class ActivityPub::OutboxesController < Api::BaseController
 
   before_action :set_account
   before_action :set_statuses
+  before_action :set_cache_headers
 
   def show
+    unless page_requested?
+      skip_session!
+      expires_in 1.minute, public: true
+    end
+
     render json: outbox_presenter, serializer: ActivityPub::OutboxSerializer, adapter: ActivityPub::Adapter, content_type: 'application/activity+json'
   end