* Allow admins to suggest default users to follow during onboarding
Allows the onboarding "follow users" slide to be configured by admins.
Closes https://github.com/thepracticaldev/dev.to/issues/7106.
* Remove redundant safety checks, refactor specs
* Add explicit note about how suggested users are used in onboarding
* Some configs_controller cleanup and fix copypasta in configs/show template
* Fetch SiteConfig.suggested_users via before_action
* Use presence instead of empty?
