Followers-only post federation (#2111)

* Make private toots get PuSHed to subscription URLs that belong to domains where you have approved followers

* Authorized followers controller, stub for bulk action

* Soft block in the background

* Add simple test for new controller

* Rename Settings::FollowersController to Settings::FollowerDomainsController, paginate results,
rename "private" post setting to "followers-only", fix pagination style, improve post privacy
preferences style, improve warning style

* Extract compose form warnings into own container, show warning when posting to followers-only with unlocked account

config/routes.rb

@@ -63,6 +63,8 @@ Rails.application.routes.draw do
       resources :recovery_codes, only: [:create]
       resource :confirmation, only: [:new, :create]
     end
+
+    resource :follower_domains, only: [:show, :update]
   end
 
   resources :media, only: [:show]
@@ -109,9 +111,7 @@ Rails.application.routes.draw do
     # 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