Create Redisable#redis (#9633)

* Create Redisable

* Use #redis instead of Redis.current

app/lib/activitypub/activity.rb

@@ -2,6 +2,7 @@
 
 class ActivityPub::Activity
   include JsonLdHelper
+  include Redisable
 
   def initialize(json, account, **options)
     @json    = json
@@ -70,10 +71,6 @@ class ActivityPub::Activity
     @object_uri ||= value_or_id(@object)
   end
 
-  def redis
-    Redis.current
-  end
-
   def distribute(status)
     crawl_links(status)