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

Conflicts:
	app/controllers/application_controller.rb

Changed instance theme selection by instance flavour selection.

app/views/layouts/application.html.haml

@@ -21,6 +21,9 @@
         = javascript_pack_tag "locales/#{@theme[:flavour]}/en", integrity: true, crossorigin: 'anonymous'
     = csrf_meta_tags
 
+    - if Setting.custom_css.present?
+      = stylesheet_link_tag custom_css_path, media: 'all'
+
     = yield :header_tags
 
     -#  These must come after :header_tags to ensure our initial state has been defined.

app/views/layouts/public.html.haml

@@ -11,7 +11,7 @@
             = link_to t('settings.back'), root_url, class: 'nav-link nav-button webapp-btn'
           - else
             = link_to t('auth.login'), new_user_session_path, class: 'webapp-btn nav-link nav-button'
-            = link_to t('auth.register'), new_user_registration_path, class: 'webapp-btn nav-link nav-button'
+            = link_to t('auth.register'), open_registrations? ? new_user_registration_path : 'https://joinmastodon.org/#getting-started', class: 'webapp-btn nav-link nav-button'
 
     .container= yield