cmd/k8s-operator: add nodeSelector to DNSConfig resource (#19429)

This commit modifies the `DNSConfig` resource to allow customisation of
the `spec.nodeSelector` field in the nameserver pods.

Closes: https://github.com/tailscale/tailscale/issues/19419

Signed-off-by: David Bond <davidsbond93@gmail.com>

k8s-operator/api.md

@@ -484,6 +484,7 @@ _Appears in:_
 | --- | --- | --- | --- |
 | `tolerations` _[Toleration](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.3/#toleration-v1-core) array_ | If specified, applies tolerations to the pods deployed by the DNSConfig resource. |  |  |
 | `affinity` _[Affinity](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.3/#affinity-v1-core)_ | If specified, applies affinity rules to the pods deployed by the DNSConfig resource. |  |  |
+| `nodeSelector` _object (keys:string, values:string)_ | If specified, applies node selector rules to the pods deployed by the DNSConfig resource. |  |  |
 
 
 #### NameserverService

k8s-operator/apis/v1alpha1/types_tsdnsconfig.go

@@ -116,6 +116,9 @@ type NameserverPod struct {
 	// If specified, applies affinity rules to the pods deployed by the DNSConfig resource.
 	// +optional
 	Affinity *corev1.Affinity `json:"affinity,omitzero"`
+	// If specified, applies node selector rules to the pods deployed by the DNSConfig resource.
+	// +optional
+	NodeSelector map[string]string `json:"nodeSelector,omitzero"`
 }
 
 type DNSConfigStatus struct {

k8s-operator/apis/v1alpha1/zz_generated.deepcopy.go

@@ -474,6 +474,13 @@ func (in *NameserverPod) DeepCopyInto(out *NameserverPod) {
 		*out = new(corev1.Affinity)
 		(*in).DeepCopyInto(*out)
 	}
+	if in.NodeSelector != nil {
+		in, out := &in.NodeSelector, &out.NodeSelector
+		*out = make(map[string]string, len(*in))
+		for key, val := range *in {
+			(*out)[key] = val
+		}
+	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new NameserverPod.