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.

app/controllers/settings/identity_proofs_controller.rb

@@ -22,8 +22,7 @@ class Settings::IdentityProofsController < Settings::BaseController
     if current_account.username.casecmp(params[:username]).zero?
       render layout: 'auth'
     else
-      flash[:alert] = I18n.t('identity_proofs.errors.wrong_user', proving: params[:username], current: current_account.username)
-      redirect_to settings_identity_proofs_path
+      redirect_to settings_identity_proofs_path, alert: I18n.t('identity_proofs.errors.wrong_user', proving: params[:username], current: current_account.username)
     end
   end
 
@@ -35,11 +34,16 @@ class Settings::IdentityProofsController < Settings::BaseController
       PostStatusService.new.call(current_user.account, text: post_params[:status_text]) if publish_proof?
       redirect_to @proof.on_success_path(params[:user_agent])
     else
-      flash[:alert] = I18n.t('identity_proofs.errors.failed', provider: @proof.provider.capitalize)
-      redirect_to settings_identity_proofs_path
+      redirect_to settings_identity_proofs_path, alert: I18n.t('identity_proofs.errors.failed', provider: @proof.provider.capitalize)
     end
   end
 
+  def destroy
+    @proof = current_account.identity_proofs.find(params[:id])
+    @proof.destroy!
+    redirect_to settings_identity_proofs_path, success: I18n.t('identity_proofs.removed')
+  end
+
   private
 
   def check_enabled