Add Rails 8 authentication generator

[jeromedalbert]

Fixes #2810.

Problem

When running Rails 8's bin/rails generate authentication, generation ends with with the following error: error rspec [not found].

This is because the Rails AuthenticationGenerator contains hook_for :test_framework, which calls rspec-rails, but it errors out since rspec-rails does not have an authentication generator.

Solution

Add authentication generator that creates a user test and possibly a fixture, similarly to Rails' TestUnit::Generators::AuthenticationGenerator. The fixture is basically the same as the Rails one except that it has a comment similar to rspec-rails' model fixture.

An alternative solution could be to somehow disable the authentication generator for rspec-rails so nothing is generated while not having any errors. This might be a viable option if Rails adds more generators in the future and playing catch-up is undesired.

[JonRowe]

I think this is a good start, I'm sort of wondering if it makes sense to add some scaffold specs showing that login works but I think I'm right in thinking the generator as is doesn't generate any tests at all?

[jeromedalbert]

I think I'm right in thinking the generator as is doesn't generate any tests at all?

Correct, the Rails 8 generator doesn't generate any controller or integration or system tests or anything, I guess the Rails team decided to leave these as an exercise for the user. The only test it generates is an empty test/models/user_test.rb ActiveSupport::TestCase, and a fixture. So this PR is doing the same in the RSpec world.

I think that if Rails generates more tests in a future version, such as login tests, then the same could be done in rspec-rails.

[JonRowe]

Thanks!