Customizing authentication after soft deleting user by Discard gem in Ruby on Rails

Question

I'm working on deleting users created by Devise with Discard; My issue is after deleting a user I want to customize the authentication:

This user shouldn't be able to login, but he should be able to register again with the same email.

In Discard documentation; they mentioned overriding active_for_authentication method in User model:

class User < ActiveRecord::Base
  def active_for_authentication?
    super && !discarded?
  end
end

but this prevents both login and register.

Is there any other way to fix that?

I'm using:

gem "rails", "~> 6.1.4.1"
gem "discard", '~> 1.2'
gem "devise", "~> 4.8.0"