Merge commit '877090518682b6c77ba9bdfa0231afd56daec44d' into glitch-soc/merge-upstream

Conflicts:
- `app/models/concerns/user/has_settings.rb`:
  Not a real conflict, upstream added a setting textually close to a glitch-soc one.
  Added upstream's new setting.
- `app/views/settings/preferences/appearance/show.html.haml`:
  Not a real conflict, upstream added a setting textually close to a glitch-soc one.
  Added upstream's new setting.
- `config/routes.rb`:
  Upstream moved web app routes to `config/routes/web_app.rb`, while glitch-soc had
  an extra route.
  Moved the extra route to `config/routes/web_app.rb`.
- `spec/controllers/settings/preferences/appearance_controller_spec.rb`:
  This spec got converted to a system spec upstream.
  However, the theme setting works differently in glitch-soc, so the spec had been
  changed.
  Changed the corresponding system spec as well.

app/validators/domain_validator.rb

@@ -4,7 +4,7 @@ class DomainValidator < ActiveModel::EachValidator
   MAX_DOMAIN_LENGTH = 256
   MIN_LABEL_LENGTH = 1
   MAX_LABEL_LENGTH = 63
-  ALLOWED_CHARACTERS_RE = /^[a-z0-9\-]+$/i
+  ALLOWED_CHARACTERS_RE = /^[a-z0-9-]+$/i
 
   def validate_each(record, attribute, value)
     return if value.blank?