RSpec for Rails 8 Authentication

[BlazingRockStorm]

Rails 8 introduces a basic authentication generator with the default test file:

test/mailers/previews/passwords_mailer_preview.rb

It just the password mailer test by Minitest

I think it is a good idea to add RSpec generator for Rails 8 built-in authenticator.

For the time being, the tests is only for sign in, sign out and reset password features.

If being approved by the RSpec team, I will make a pull request.

[pirj]

Sounds like a reasonable addition. A PR is welcome.

[JonRowe]

This was added in #2811 it just hasn't been released yet