def authenticate(params)
      credentials = Authenticate.configuration.user_model_class.credentials(params)
      Authenticate.configuration.user_model_class.authenticate(credentials)
    end
def authenticate(params)
      credentials = Authenticate.configuration.user_model_class.credentials(params)
      Authenticate.configuration.user_model_class.authenticate(credentials)
    end
Validate a user's identity with (typically) email/ID & password, and return the User if valid, or nil.
 After calling this, call login(user) to complete the process.