Added Rspec authentication tests

[Warsama-Gabriel]

Added authentication tests for SessionsController and OmniAuth Shibboleth integration

• Implemented tests for SessionsController actions, covering both production and development environments.
• Mocked Shibboleth OmniAuth responses to test authentication flows in production.
• Enhanced User model tests to validate user creation and attributes.
• Updated OmniAuth configuration tests to ensure provider settings are correctly applied.

[srbbins]

@mfall3 I think this looks good, but you have a lot more experience writing tests in Rails apps than me. Do you have any feedback on this PR?

[mfall3]

It is recommended to use OmniAuth.config.test_mode in the test. https://gorails.com/blog/how-to-test-omniauth-params

[mfall3]

As part of authorization, but looking ahead to next tests (authorization-based), we will want to mock sign_in (or login) specifically.
https://github.com/medusa-project/databank/blob/main/spec/support/omniauth_macros.rb
The pattern here should also work for the :shibboleth provider

[Warsama-Gabriel]

@mfall3 That makes sense. Using OmniAuth's add_mock method with config.test_mode = true would better simulate mocking user authentication rather than directly setting the request.env['omniauth.auth'] hash directly. I'll go ahead and update the PR to reflect those changes.

[mfall3]

The sign_in or login OmniAuth testing mode method can be added in the future if needed for other tests. I am fine with this pull request going forward.