FEATURE: Arbitrary validations for site settings

lib/site_setting_validations.rb

@@ -0,0 +1,17 @@
+
+module SiteSettingValidations
+
+  def validate_error(key)
+    raise Discourse::InvalidParameters.new(I18n.t("errors.site_settings.#{key}"))
+  end
+
+  def validate_min_username_length(new_val)
+    validate_error :min_username_length_range if new_val > SiteSetting.max_username_length
+    validate_error :min_username_length_exists if User.where('length(username) < ?', new_val).exists?
+  end
+
+  def validate_max_username_length(new_val)
+    validate_error :min_username_length_range if new_val < SiteSetting.min_username_length
+    validate_error :max_username_length_exists if User.where('length(username) > ?', new_val).exists?
+  end
+end