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

Conflicts:
- `app/javascript/mastodon/features/compose/components/poll_form.js`:
  Upstream bumped poll option character limit, but we already had
  a higher one, kept ours.
- `app/validators/poll_validator.rb`:
  Upstream bumped poll option character limit, but we already had
  a higher one, kept ours.
- `config/initializers/content_security_policy.rb`:
  Upstream added a rule, the way we compute ours is different, but
  that added rule has been ported.
- `package.json`:
  No real conflict, dependency update. Performed the same update.
- `yarn.lock`:
  No real conflict, dependency update. Performed the same update.

lib/mastodon/media_cli.rb

@@ -115,7 +115,7 @@ module Mastodon
       when :filesystem
         require 'find'
 
-        root_path = ENV.fetch('RAILS_ROOT_PATH', File.join(':rails_root', 'public', 'system')).gsub(':rails_root', Rails.root.to_s)
+        root_path = ENV.fetch('PAPERCLIP_ROOT_PATH', File.join(':rails_root', 'public', 'system')).gsub(':rails_root', Rails.root.to_s)
 
         Find.find(File.join(*[root_path, prefix].compact)) do |path|
           next if File.directory?(path)