Refactor controllers for statuses, accounts, and more (#11249)

app/controllers/activitypub/outboxes_controller.rb

@@ -4,8 +4,8 @@ class ActivityPub::OutboxesController < Api::BaseController
   LIMIT = 20
 
   include SignatureVerification
+  include AccountOwnedConcern
 
-  before_action :set_account
   before_action :set_statuses
   before_action :set_cache_headers
 
@@ -17,10 +17,6 @@ class ActivityPub::OutboxesController < Api::BaseController
 
   private
 
-  def set_account
-    @account = Account.find_local!(params[:account_username])
-  end
-
   def outbox_presenter
     if page_requested?
       ActivityPub::CollectionPresenter.new(