def validate_config!
      VALIDATABLE_ATTRIBUTES.each do |attr|
        klass = CONFIG_ATTRIBUTES_TO_HEADER_CLASSES[attr]
        klass.validate_config!(instance_variable_get("@#{attr}"))
      end
    end
def validate_config!
      VALIDATABLE_ATTRIBUTES.each do |attr|
        klass = CONFIG_ATTRIBUTES_TO_HEADER_CLASSES[attr]
        klass.validate_config!(instance_variable_get("@#{attr}"))
      end
    end
Public: validates all configurations values.

 Raises various configuration errors if any invalid config is detected.

 Returns nothing