feat: add support for excluding or setting the default agent serviceA…

[h0tw1r3]

What does this PR do?

Decouples the default template serviceAccount from serviceAccountAgent.name.

Basically I found myself wanting to set the agent.defaultsProviderTemplate to default, and also the ability to exclude the serviceAccount from the autogenerated default template.

Submitter checklist

• I bumped the "version" key in ./charts/jenkins/Chart.yaml.
• I added a new changelog entry to ./charts/jenkins/CHANGELOG.md.
• I followed the technical requirements.
• I ran .github/helm-docs.sh from the project root.

[h0tw1r3]

Does this seem worthwhile, or am I going in completely the wrong direction (or both)? :)

[timja]

hmm I'm a little confused, won't it use the default one by default if you don't specify create https://github.com/jenkinsci/helm-charts/blob/main/charts/jenkins/templates/_helpers.tpl#L565-L568

[h0tw1r3]

hmm I'm a little confused, won't it use the default one by default if you don't specify create https://github.com/jenkinsci/helm-charts/blob/main/charts/jenkins/templates/_helpers.tpl#L565-L568

It does, but if you also set agent.defaultsProviderTemplate: "default", it's impossible for jobs to override the serviceAccountName.

For example, if you set the agent.defaultsProviderTemplate: "default", and need a pod with a different serviceAccountName, something like this:

Jenkinsfile

pipeline {
    agent {
        kubernetes {
            yaml '''
                apiVersion: v1
                kind: Pod
                spec:
                    serviceAccountName: other-account
                    containers:
                    - name: dind
                      image: docker:dind
                      securityContext:
                        privileged: true
                '''
        }
    }
}

When the job runs and the yaml get's merged with the "default" template, serviceAccountName is never overridden no matter what I set inheritYamlMergeStrategy or yamlMergeStrategy to in the "default" pod template.

Perhaps this is intended behavior? This PR just gives the ability to not add the servicecAccountName to the "default" pod template.

[timja]

sure sounds fine then if you can make the build pass