Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- Gemfile
- app/controllers/api/v1/search_controller.rb
  Conflict because we changed the number of default results to be
  configurable
- app/lib/settings/scoped_settings.rb
  Addition of a new “noindex” site-wide setting,
  conflict due to our change of the two other site-wide settings
  (default flavour and skin instead of theme)
- spec/controllers/application_controller_spec.rb
  Addition of a new “noindex” site-wide setting,
  conflict due to our change of the two other site-wide settings
  (default flavour and skin instead of theme)

app/controllers/api/v1/timelines/public_controller.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 class Api::V1::Timelines::PublicController < Api::BaseController
+  before_action :require_user!, only: [:show], if: :require_auth?
   after_action :insert_pagination_headers, unless: -> { @statuses.empty? }
 
   respond_to :json
@@ -12,6 +13,10 @@ class Api::V1::Timelines::PublicController < Api::BaseController
 
   private
 
+  def require_auth?
+    !Setting.timeline_preview
+  end
+
   def load_statuses
     cached_public_statuses
   end