Add notifications of severed relationships (#27511)

config/locales/en.yml

@@ -1660,10 +1660,22 @@ en:
     preferences: Preferences
     profile: Public profile
     relationships: Follows and followers
+    severed_relationships: Severed relationships
     statuses_cleanup: Automated post deletion
     strikes: Moderation strikes
     two_factor_authentication: Two-factor Auth
     webauthn_authentication: Security keys
+  severed_relationships:
+    download: Download (%{count})
+    event_type:
+      account_suspension: Account suspension (%{target_name})
+      domain_block: Server suspension (%{target_name})
+      user_domain_block: You blocked %{target_name}
+    lost_followers: Lost followers
+    lost_follows: Lost follows
+    preamble: You may lose follows and followers when you block a domain or when your moderators decide to suspend a remote server. When that happens, you will be able to download lists of severed relationships, to be inspected and possibly imported on another server.
+    purged: Information about this server has been purged by your server's administrators.
+    type: Event
   statuses:
     attached:
       audio:

config/navigation.rb

@@ -16,7 +16,11 @@ SimpleNavigation::Configuration.run do |navigation|
       s.item :other, safe_join([fa_icon('cog fw'), t('preferences.other')]), settings_preferences_other_path
     end
 
-    n.item :relationships, safe_join([fa_icon('users fw'), t('settings.relationships')]), relationships_path, if: -> { current_user.functional? && !self_destruct }
+    n.item :relationships, safe_join([fa_icon('users fw'), t('settings.relationships')]), relationships_path, if: -> { current_user.functional? && !self_destruct } do |s|
+      s.item :current, safe_join([fa_icon('users fw'), t('settings.relationships')]), relationships_path
+      s.item :severed_relationships, safe_join([fa_icon('unlink fw'), t('settings.severed_relationships')]), severed_relationships_path
+    end
+
     n.item :filters, safe_join([fa_icon('filter fw'), t('filters.index.title')]), filters_path, highlights_on: %r{/filters}, if: -> { current_user.functional? && !self_destruct }
     n.item :statuses_cleanup, safe_join([fa_icon('history fw'), t('settings.statuses_cleanup')]), statuses_cleanup_path, if: -> { current_user.functional_or_moved? && !self_destruct }
 

config/routes.rb

@@ -189,6 +189,14 @@ Rails.application.routes.draw do
   end
 
   resource :relationships, only: [:show, :update]
+  resources :severed_relationships, only: [:index] do
+    member do
+      constraints(format: :csv) do
+        get :followers
+        get :following
+      end
+    end
+  end
   resource :statuses_cleanup, controller: :statuses_cleanup, only: [:show, :update]
 
   get '/media_proxy/:id/(*any)', to: 'media_proxy#show', as: :media_proxy, format: false