Change “Posting defaults” settings page to enforce nobody quote policy for private default visibility (#36040)

app/controllers/settings/preferences/posting_defaults_controller.rb

@@ -6,4 +6,10 @@ class Settings::Preferences::PostingDefaultsController < Settings::Preferences::
   def after_update_redirect_path
     settings_preferences_posting_defaults_path
   end
+
+  def user_params
+    super.tap do |params|
+      params[:settings_attributes][:default_quote_policy] = 'nobody' if params[:settings_attributes][:default_privacy] == 'private'
+    end
+  end
 end