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

Conflicts:
- .eslintrc.yml
  Removed, as upstream removed it.
- app/controllers/admin/statuses_controller.rb
  Minor code cleanup when porting one of our features.
- app/models/account.rb
  Note length validation has changed upstream.
  We now use upstream's validation (dropped legacy glitch-soc
  account metadata stuff) but with configurable limit.
- app/services/post_status_service.rb
  Upstream has added support for scheduled toots, refactoring
  the code a bit. Adapted our changes to this refactoring.
- app/views/stream_entries/_detailed_status.html.haml
  Not a real conflict, changes too close.
- app/views/stream_entries/_simple_status.html.haml
  Not a real conflict, changes too close.

config/initializers/paperclip.rb

@@ -25,7 +25,7 @@ if ENV['S3_ENABLED'] == 'true'
     s3_protocol: s3_protocol,
     s3_host_name: s3_hostname,
     s3_headers: {
-      'Cache-Control' => 'max-age=315576000',
+      'Cache-Control' => 'public, max-age=315576000, immutable',
     },
     s3_permissions: ENV.fetch('S3_PERMISSION') { 'public-read' },
     s3_region: s3_region,