[lbarrosby]

Why is this pull request needed and what does it do?

port is optional on a server block (the configmap already handles it, and CoreDNS picks the default for the scheme), but the port helpers call toString .port unconditionally. Without a port the chart renders:

ports:
- {"name":"udp-<nil>","port":null,"protocol":"UDP","targetPort":0}
...
- {"containerPort":0,"name":"udp-<nil>","protocol":"UDP"}

which the API server rejects. This adds a small coredns.serverPort helper that returns .port when set, otherwise the CoreDNS default for the first zone's scheme (53, 853 for tls:///quic://, 443 for grpc:///https://), and uses it in both coredns.servicePorts and coredns.containerPorts. servicePort still overrides the Service port.

Rendering with the default values is byte for byte the same as before. Added unit tests for the Service and the Deployment with port-less server blocks (they fail without the fix), and updated the port comment in values.yaml.

Which issues (if any) are related?

Fixes #67

Checklist:

• I have bumped the chart version according to versioning.
• I have updated the chart changelog with all the changes that come with this pull request according to changelog.
• Any new values are backwards compatible and/or have sensible default.
• I have signed off all my commits as required by DCO.

Changes are automatically published when merged to main. They are not published on branches.

Note on DCO

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[hagaibarel]

Thanks for the PR!