Add support for optional node selector labels for kube-ovn OVS/OVN pods

[saeed-mcu]

This change introduces a new Helm value ovsNodesLabels that allows adding custom node selector labels to ovs-ovn pods. For example:

 ovsNodesLabels:
  kube-ovn/role: ovs

This is useful in environments such as OpenStack-Helm, where operators may want to schedule OVS/OVN pods only on specific nodes (e.g., compute nodes) instead of deploying them cluster-wide. When ovsNodesLabels is empty, only the default selector kubernetes.io/os: linux is applied.

[gemini-code-assist]

Summary of Changes

Hello @saeed-mcu, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new Helm configuration option, ovsNodesLabels, which provides greater control over where Kube-OVN's OVS/OVN pods are scheduled within a Kubernetes cluster. This enhancement allows users to define custom node selector labels, facilitating more precise deployment strategies, especially in environments requiring specific pod placement on designated node types.

Highlights

• Custom Node Selection: Introduces a new Helm value ovsNodesLabels to allow custom node selector labels for ovs-ovn pods, enhancing deployment flexibility.
• Targeted Pod Scheduling: Enables operators to schedule OVS/OVN pods on specific nodes, which is particularly useful in environments like OpenStack-Helm for placing pods on designated compute nodes.
• Default Behavior Maintained: When the ovsNodesLabels value is empty, the default kubernetes.io/os: linux selector is still applied, ensuring basic functionality.

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[gemini-code-assist]

Code Review

This pull request adds a new Helm value ovsNodesLabels to allow specifying node selector labels for OVS/OVN pods. While the feature is useful, the implementation has a few critical issues. The default value for ovsNodesLabels in values.yaml is an empty list ([]), which will cause Helm to generate invalid Kubernetes manifests. Additionally, the way the labels are rendered in the DaemonSet templates is not robust and will also fail when the value is not provided or is an empty map. I've provided suggestions to fix these issues by changing the default value to an empty map ({}), updating the misleading comments, and using a with block in the templates for safer rendering.

[gemini-code-assist]

The current implementation for adding ovsNodesLabels is not robust and will generate invalid YAML, causing deployment failure. If ovsNodesLabels is not provided, it will be nil, and toYaml will render null, which is invalid in this context. Using a with block ensures that labels are only rendered if the ovsNodesLabels map is not empty, preventing this error.

        {{- with .Values.ovsNodesLabels }}
{{- toYaml . | nindent 8 }}
        {{- end }}

[gemini-code-assist]

The current implementation for adding ovsNodesLabels is not robust and will generate invalid YAML, causing deployment failure. If ovsNodesLabels is not provided, it will be nil, and toYaml will render null, which is invalid in this context. Using a with block ensures that labels are only rendered if the ovsNodesLabels map is not empty, preventing this error.

        {{- with .Values.ovsNodesLabels }}
{{- toYaml . | nindent 8 }}
        {{- end }}

[gemini-code-assist]

The current implementation for adding ovsNodesLabels is not robust and will generate invalid YAML, causing deployment failure. If ovsNodesLabels is not provided, it will be nil, and toYaml will render null, which is invalid in this context. Using a with block ensures that labels are only rendered if the ovsNodesLabels map is not empty, preventing this error.

        {{- with .Values.ovsNodesLabels }}
{{- toYaml . | nindent 8 }}
        {{- end }}

[gemini-code-assist]

The new ovsNodesLabels value has an incorrect default and a misleading comment, which will cause the chart deployment to fail.

1. The default value is [] (an empty list), but it should be a map of labels. Using a list will cause template rendering to fail. The default should be {} (an empty map).
2. The comment is incorrect. It states that this feature uses Helm's lookup function, which is not the case. The labels are directly added to the nodeSelector. The comment should be updated to accurately describe its purpose.

# -- Additional node selector labels for the OVS/OVN pods.
# This allows scheduling pods like ovs-ovn, kube-ovn-cni, and kube-ovn-pinger on specific nodes.
# See https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#nodeselector
# @section -- Global parameters
ovsNodesLabels: {}
  # kube-ovn/role: ovs