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

Conflicts:
- app/controllers/admin/base_controller.rb
- app/controllers/filters_controller.rb
- app/controllers/invites_controller.rb
- app/controllers/settings/deletes_controller.rb
- app/controllers/settings/exports_controller.rb
- app/controllers/settings/follower_domains_controller.rb
- app/controllers/settings/migrations_controller.rb
- app/controllers/settings/notifications_controller.rb
- app/controllers/settings/preferences_controller.rb
- app/controllers/settings/two_factor_authentication/recovery_codes_controller.rb
- app/javascript/packs/public.js
- app/views/settings/profiles/show.html.haml

Conflicts were mostly due to the addition of body classes to the settings page,
this was caused by rejecting upstream changes for most of those files and
modifying Settings::BaseController instead.

Another cause of conflicts was the deletion of client-side checking of
display name / bio length, this was modified in app/javascript/core/settings.js
instead.

app/javascript/mastodon/features/compose/components/compose_form.js

@@ -89,7 +89,7 @@ class ComposeForm extends ImmutablePureComponent {
       return;
     }
 
-    this.props.onSubmit(this.context.router.history);
+    this.props.onSubmit(this.context.router ? this.context.router.history : null);
   }
 
   onSuggestionsClearRequested = () => {