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

Conflicts:
- `Gemfile.lock`:
  Not a real conflict, just a glitch-soc-only dependency too close to a
  dependency that got updated upstream. Updated as well.
- `app/models/status.rb`:
  Not a real conflict, just a change too close to glitch-soc-changed code
  for optionally showing boosts in public timelines.
  Applied upstream changes.
- `app/views/layouts/application.html.haml`:
  Upstream a new, static CSS file, conflict due to glitch-soc's theming
  system, include the file regardless of the theme.
- `config/initializers/content_security_policy.rb`:
  Upstream dropped 'unsafe-inline' from the 'style-src' directive, but
  both files are very different. Removed 'unsafe-inline' as well.

config/routes.rb

@@ -130,7 +130,7 @@ Rails.application.routes.draw do
       resource :confirmation, only: [:new, :create]
     end
 
-    resources :identity_proofs, only: [:index, :show, :new, :create, :update]
+    resources :identity_proofs, only: [:index, :new, :create, :destroy]
 
     resources :applications, except: [:edit] do
       member do