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

Conflicts:
- `Gemfile`:
  We updated httplog in a separate commit.
  Took upstream's change which updated it further.
- `Gemfile.lock`:
  We updated httplog in a separate commit.
  Took upstream's change which updated it further.
- `app/lib/sanitize_config.rb`:
  Upstream added better unsupported link stripping,
  while we had different sanitizing configs.
  Took only upstream's link stripping code.
- `config/locales/simple_form.pl.yml`:
  Strings unused in glitch-soc had been removed from
  glitch-soc, reintroduced them even if they are not
  useful, to reduce the risk of later merge conflicts.

Gemfile

@@ -61,7 +61,7 @@ gem 'htmlentities', '~> 4.3'
 gem 'http', '~> 4.3'
 gem 'http_accept_language', '~> 2.1'
 gem 'http_parser.rb', '~> 0.6', git: 'https://github.com/tmm1/http_parser.rb', ref: '54b17ba8c7d8d20a16dfc65d1775241833219cf2', submodules: true
-gem 'httplog', '~> 1.4.1'
+gem 'httplog', '~> 1.4.2'
 gem 'idn-ruby', require: 'idn'
 gem 'kaminari', '~> 1.1'
 gem 'link_header', '~> 0.0'