module Devise::Models::Authenticatable

def valid_for_authentication?

and inactive_message instead.
However, you should not overwrite this method, you should overwrite active_for_authentication?

if a model should be signed in or not.
find_for_authentication are the methods used in a Warden::Strategy to check
Check if the current object is valid for authentication. This method and
def valid_for_authentication?
  block_given? ? yield : true
end