Merge commit '379115e601361c2b5da775fbf28b7dff9dc02e71' into glitch-soc/merge-upstream

Conflicts:
- `config/navigation.rb`:
  Conflict due to glitch-soc having extra navigation items for its theming
  system.
  Ported upstream changes.

app/controllers/application_controller.rb

@@ -13,6 +13,7 @@ class ApplicationController < ActionController::Base
   include ThemingConcern
   include DatabaseHelper
   include AuthorizedFetchHelper
+  include SelfDestructHelper
 
   helper_method :current_account
   helper_method :current_session
@@ -41,6 +42,8 @@ class ApplicationController < ActionController::Base
     service_unavailable
   end
 
+  before_action :check_self_destruct!
+
   before_action :store_referrer, except: :raise_not_found, if: :devise_controller?
   before_action :require_functional!, if: :user_signed_in?
 
@@ -169,6 +172,15 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  def check_self_destruct!
+    return unless self_destruct?
+
+    respond_to do |format|
+      format.any  { render 'errors/self_destruct', layout: 'auth', status: 410, formats: [:html] }
+      format.json { render json: { error: Rack::Utils::HTTP_STATUS_CODES[410] }, status: code }
+    end
+  end
+
   def set_cache_control_defaults
     response.cache_control.replace(private: true, no_store: true)
   end