specifying runAsUser 0 in additionalContainers is treated as false

[SampsonCrowley]

Describe the bug

specifying a root user runner for images that require it is ignored.

helm-charts/charts/jenkins/templates/_helpers.tpl

Lines 468 to 473 in 13a4e96

	{{- if or $additionalContainers.runAsUser $.Values.agent.runAsUser }}
	runAsUser: {{ $additionalContainers.runAsUser | default $.Values.agent.runAsUser }}
	{{- end }}
	{{- if or $additionalContainers.runAsGroup $.Values.agent.runAsGroup }}
	runAsGroup: {{ $additionalContainers.runAsGroup | default $.Values.agent.runAsGroup }}
	{{- end }}

this only does a falsey check which will always return false for 0

Version of Helm and Kubernetes

- Helm: version.BuildInfo{Version:"v3.18.3", GitCommit:"6838ebcf265a3842d1433956e8a622e3290cf324", GitTreeState:"clean", GoVersion:"go1.24.4"}
- Kubernetes:
  Client Version: v1.34.1
  Kustomize Version: v5.4.2
  Server Version: v1.33.5-eks-113cf36

Chart version

5.8.64

What happened?

1. set additionalContainer[0].runAsUser = 0
2. no value is set at all in deployed config
3. does not need a truthy global runAsUser to reproduce

What you expected to happen?

the additional container should explicitly set 0

How to reproduce it

agent:
  additionalContainers:
    - sideContainerName: dind
      image:
        repository: docker
        tag: 26-dind
      command: dockerd-entrypoint.sh
      runAsUser: 0

Anything else we need to know?

Related issues: helm/helm#3164

Seems as though the correct solution would be to call toString <optionalvalue> to guarantee explicit 0 is parsed correctly

using runAsUser: "0" seems to work

[SampsonCrowley]

Thinking about it further this also would apply to additionalAgents for the same reason