ActivityPub: Add basic, read-only support for Outboxes, Notes, and Create/Announce Activities (#2197)

* Clean up collapsible components

* Expose user Outboxes and AS2 representations of statuses

* Save work thus far.

* Fix bad merge.

* Save my work

* Clean up pagination.

* First test working.

* Add tests.

* Add Forbidden error template.

* Revert yarn.lock changes.

* Fix code style deviations and use localized instead of hardcoded English text.

config/routes.rb

@@ -106,6 +106,15 @@ Rails.application.routes.draw do
     # OEmbed
     get '/oembed', to: 'oembed#show', as: :oembed
 
+    # ActivityPub
+    namespace :activitypub do
+      get '/users/:id/outbox', to: 'outbox#show', as: :outbox
+
+      get '/statuses/:id', to: 'activities#show_status', as: :status
+
+      resources :notes, only: [:show]
+    end
+
     # JSON / REST API
     namespace :v1 do
       resources :statuses, only: [:create, :show, :destroy] do