Add support for autoscaling to/from 0

Introduce support for autoscaling to/from 0 based on cluster-api
contract. For this:
- introduce a new controller for OSMT that updates status with
  capacity and nodeinfo
- update e2e tests to include autoscaling scenario
- add feature behind a featureGate
- add a documentation page

Author: nikParasyr

Makefile

@@ -195,7 +195,8 @@ e2e-templates: $(addprefix $(E2E_NO_ARTIFACT_TEMPLATES_DIR)/, \
 		 cluster-template-no-bastion.yaml \
 		 cluster-template-health-monitor.yaml \
 		 cluster-template-capi-v1beta1.yaml \
-		 cluster-template-cluster-identity.yaml)
+		 cluster-template-cluster-identity.yaml \
+		 cluster-template-topology-autoscaler.yaml)
 # Currently no templates that require CI artifacts
 # $(addprefix $(E2E_TEMPLATES_DIR)/, add-templates-here.yaml) \
 
@@ -333,6 +334,7 @@ generate-codegen: generate-controller-gen $(OPENAPI_GEN) $(APPLYCONFIGURATION_GE
 		k8s.io/api/core/v1 \
 		k8s.io/apimachinery/pkg/apis/meta/v1 \
 		k8s.io/apimachinery/pkg/runtime \
+		k8s.io/apimachinery/pkg/api/resource \
 		k8s.io/apimachinery/pkg/version
 	@echo "** Generating openapi.json **"
 	go run ./cmd/models-schema | jq > ./openapi.json

api/v1beta1/openstackmachinetemplate_types.go

@@ -17,6 +17,7 @@ limitations under the License.
 package v1beta1
 
 import (
+	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
@@ -25,17 +26,39 @@ type OpenStackMachineTemplateSpec struct {
 	Template OpenStackMachineTemplateResource `json:"template"`
 }
 
+// OpenStackMachineTemplateStatus defines the observed state of OpenStackMachineTemplate.
+type OpenStackMachineTemplateStatus struct {
+	// Capacity defines the resource capacity for this machine.
+	// This value is used for autoscaling from zero operations as defined in:
+	// https://github.com/kubernetes-sigs/cluster-api/blob/main/docs/proposals/20210310-opt-in-autoscaling-from-zero.md
+	// +optional
+	Capacity corev1.ResourceList `json:"capacity,omitempty"`
+	// +optional
+	NodeInfo NodeInfo `json:"nodeInfo,omitempty,omitzero"`
+}
+
+// NodeInfo contains information about the node's architecture and operating system.
+// +kubebuilder:validation:MinProperties=1
+type NodeInfo struct {
+	// operatingSystem is a string representing the operating system of the node.
+	// This may be a string like 'linux' or 'windows'.
+	// +optional
+	OperatingSystem string `json:"operatingSystem,omitempty"`
+}
+
 // +genclient
 // +kubebuilder:object:root=true
 // +kubebuilder:storageversion
 // +kubebuilder:resource:path=openstackmachinetemplates,scope=Namespaced,categories=cluster-api,shortName=osmt
+// +kubebuilder:subresource:status
 
 // OpenStackMachineTemplate is the Schema for the openstackmachinetemplates API.
 type OpenStackMachineTemplate struct {
 	metav1.TypeMeta   `json:",inline"`
 	metav1.ObjectMeta `json:"metadata,omitempty"`
 
-	Spec OpenStackMachineTemplateSpec `json:"spec,omitempty"`
+	Spec   OpenStackMachineTemplateSpec   `json:"spec,omitempty"`
+	Status OpenStackMachineTemplateStatus `json:"status,omitempty"`
 }
 
 // +kubebuilder:object:root=true
@@ -50,3 +73,11 @@ type OpenStackMachineTemplateList struct {
 func init() {
 	objectTypes = append(objectTypes, &OpenStackMachineTemplate{}, &OpenStackMachineTemplateList{})
 }
+
+// GetIdentifyRef returns the object's namespace and IdentityRef if it has an IdentityRef, or nulls if it does not.
+func (r *OpenStackMachineTemplate) GetIdentityRef() (*string, *OpenStackIdentityReference) {
+	if r.Spec.Template.Spec.IdentityRef != nil {
+		return &r.Namespace, r.Spec.Template.Spec.IdentityRef
+	}
+	return nil, nil
+}

api/v1beta1/zz_generated.deepcopy.go

@@ -73,6 +73,12 @@ API rule violation: names_match,k8s.io/api/core/v1,RBDVolumeSource,RBDPool
 API rule violation: names_match,k8s.io/api/core/v1,RBDVolumeSource,RadosUser
 API rule violation: names_match,k8s.io/api/core/v1,VolumeSource,CephFS
 API rule violation: names_match,k8s.io/api/core/v1,VolumeSource,StorageOS
+API rule violation: names_match,k8s.io/apimachinery/pkg/api/resource,Quantity,Format
+API rule violation: names_match,k8s.io/apimachinery/pkg/api/resource,Quantity,d
+API rule violation: names_match,k8s.io/apimachinery/pkg/api/resource,Quantity,i
+API rule violation: names_match,k8s.io/apimachinery/pkg/api/resource,Quantity,s
+API rule violation: names_match,k8s.io/apimachinery/pkg/api/resource,int64Amount,scale
+API rule violation: names_match,k8s.io/apimachinery/pkg/api/resource,int64Amount,value
 API rule violation: names_match,k8s.io/apimachinery/pkg/apis/meta/v1,APIResourceList,APIResources
 API rule violation: names_match,k8s.io/apimachinery/pkg/apis/meta/v1,Duration,Duration
 API rule violation: names_match,k8s.io/apimachinery/pkg/apis/meta/v1,InternalEvent,Object