(feat) support explicit fsGroup

[Lerentis]

added support to explicitly define the fsGroup according to https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/pod-v1/#security-context
I know that in theory it could be overwritten in yaml declaration but there seems to be an xor with limit definitions. explicitly setting it works

Testing done

For testing i created a jenkins job with the following spec:

podTemplate(cloud: 'test', containers: [containerTemplate(args: '9999999', command: 'sleep', image: 'jenkins/inbound-agent:3248.v65ecb_254c298-5', livenessProbe: containerLivenessProbe(execArgs: '', failureThreshold: 0, initialDelaySeconds: 0, periodSeconds: 0, successThreshold: 0, timeoutSeconds: 0), name: 'jnlp', resourceLimitCpu: '', resourceLimitEphemeralStorage: '', resourceLimitMemory: '', resourceRequestCpu: '', resourceRequestEphemeralStorage: '', resourceRequestMemory: '', workingDir: '/home/jenkins/agent')], fsGroup: '1000', name: 'test', namespace: 'default') {
    node(POD_LABEL) {
        stage('test') {
            echo "hello world"
        }
    }
}

and checked if the securityContext of the resulting pod is set to the expected fsGroup:

  securityContext:
    fsGroup: 1000

which was set as expected

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[Vlatombe]

but there seems to be an xor with limit definitions

This needs a unit test.