Extract config_file method from action_class to enable external access

[Copilot]

• [x] Extract config_file method from action_class to enable external access
• [x] Add test case for config_file accessibility
• [x] Extract config_file implementation to helpers.rb (per review feedback)
• [x] Ensure external accessibility still works after refactoring
• [x] Validate syntax and logic of changes

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Copilot]

@damacus 👋 This repository doesn't have Copilot instructions. With Copilot instructions, I can understand the repository better, work faster and produce higher quality PRs.

I can generate a .github/copilot-instructions.md file for you automatically. Click here to open a pre-filled issue and assign it to me. I'll write the instructions, and then tag you for review.

[damacus]

@copilot rebase

[github-actions[bot]]

Slowest examples

Top 10 slowest examples (0.95 seconds, 27.92% of total time)

Example	Description	Time in seconds
spec/unit/resources/site_spec.rb:32	nginx_site with template is expected to create template "/etc/nginx/conf.http.d/default.conf"	0.23782
spec/unit/resources/install_spec.rb:14	nginx_install with default properties with repo source with centos platform is expected to do nothing	0.13325
spec/unit/resources/install_spec.rb:22	nginx_install with default properties with repo source with amazon platform is expected to notify "ohai[nginx]" with action :reload immediately	0.08978
spec/unit/resources/config_spec.rb:17	nginx_config with default properties is expected to create template "/etc/nginx/nginx.conf"	0.08405
spec/unit/resources/config_spec.rb:52	nginx_config with default properties is expected to create directory "/etc/nginx/conf.http.d"	0.07532
spec/unit/resources/install_spec.rb:72	nginx_install with default properties with repo source with ubuntu platform is expected to add apt_repository "nginx"	0.07412
spec/unit/resources/install_spec.rb:22	nginx_install with default properties with epel source with amazon platform is expected to notify "ohai[nginx]" with action :reload immediately	0.07172
spec/unit/resources/install_spec.rb:22	nginx_install with default properties with epel source with centos 8 platform is expected to notify "ohai[nginx]" with action :reload immediately	0.06465
spec/unit/resources/install_spec.rb:15	nginx_install with default properties with distro source with ubuntu platform is expected to create template "(?-mix:/ohai/plugins/nginx.rb)"	0.06388
spec/unit/resources/install_spec.rb:22	nginx_install with default properties with epel source with centos-stream 9 platform is expected to notify "ohai[nginx]" with action :reload immediately	0.06094