We added extend_template_helpers API methods but it does not work, methods added via this extension are not available in Foreman::Renderer. Rendering is not possible:

Create a plugin, add new method, try to use it in a template in both safemode and non-safemode. Result:

There was an error rendering the Discovery Red Hat kexec template: undefined local variable or method `discovery_kexec_kernel' for #<#<Class:0x0055f4717ade40>:0x0055f471772c28>
Did you mean?  discovery_rule_url