def authenticate!
      if u = user_class.send(config[:authenticate_method], *required_param_values)
        success!(u)
      else
        fail!(config[:error_message])
      end
    end
def authenticate!
      if u = user_class.send(config[:authenticate_method], *required_param_values)
        success!(u)
      else
        fail!(config[:error_message])
      end
    end
The workhorse.  Will pass all requred_param_values to the configured authenticate_method
 @see WardenStrategies::Simple.config
 @see Warden::Strategy::Base#authenticate!
 @api private