Merge commit 'a27bafa59653328a0f06bedb1dfb2b6ee92af43d' into glitch-soc/merge-upstream

- `app/controllers/application_controller.rb`:
  Minor conflict due to glitch-soc's theming system.
- `spec/helpers/application_helper_spec.rb`:
  Minor conflict due to glitch-soc's theming system.

app/controllers/application_controller.rb

@@ -25,7 +25,6 @@ class ApplicationController < ActionController::Base
   helper_method :use_seamless_external_login?
   helper_method :sso_account_settings
   helper_method :limited_federation_mode?
-  helper_method :body_class_string
   helper_method :skip_csrf_meta_tags?
 
   rescue_from ActionController::ParameterMissing, Paperclip::AdapterRegistry::NoHandlerError, with: :bad_request
@@ -155,10 +154,6 @@ class ApplicationController < ActionController::Base
     @current_session = SessionActivation.find_by(session_id: cookies.signed['_session_id']) if cookies.signed['_session_id'].present?
   end
 
-  def body_class_string
-    @body_classes || ''
-  end
-
   def respond_with_error(code)
     respond_to do |format|
       format.any  { render "errors/#{code}", layout: 'error', status: code, formats: [:html] }