[node operator] Add Azure client

Signed-off-by: Malte Poll <mp@edgeless.systems>

operators/constellation-node-operator/internal/azure/client/client.go

@@ -0,0 +1,45 @@
+package client
+
+import (
+	"github.com/Azure/azure-sdk-for-go/sdk/azidentity"
+	armcomputev2 "github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/compute/armcompute/v2"
+	"github.com/edgelesssys/constellation/operators/constellation-node-operator/internal/poller"
+)
+
+// Client is a client for the Azure Cloud.
+type Client struct {
+	scaleSetsAPI
+	virtualMachineScaleSetVMsAPI
+	capacityPollerGenerator func(resourceGroup, scaleSet string, wantedCapacity int64) capacityPoller
+	pollerOptions           *poller.PollUntilDoneOptions
+}
+
+// NewFromDefault creates a client with initialized clients.
+func NewFromDefault(subscriptionID, tenantID string) (*Client, error) {
+	cred, err := azidentity.NewDefaultAzureCredential(nil)
+	if err != nil {
+		return nil, err
+	}
+
+	scaleSetAPI, err := armcomputev2.NewVirtualMachineScaleSetsClient(subscriptionID, cred, nil)
+	if err != nil {
+		return nil, err
+	}
+	virtualMachineScaleSetVMsAPI, err := armcomputev2.NewVirtualMachineScaleSetVMsClient(subscriptionID, cred, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Client{
+		scaleSetsAPI:                 scaleSetAPI,
+		virtualMachineScaleSetVMsAPI: virtualMachineScaleSetVMsAPI,
+		capacityPollerGenerator: func(resourceGroup, scaleSet string, wantedCapacity int64) capacityPoller {
+			return poller.New[int64](&capacityPollingHandler{
+				resourceGroup:  resourceGroup,
+				scaleSet:       scaleSet,
+				wantedCapacity: wantedCapacity,
+				scaleSetsAPI:   scaleSetAPI,
+			})
+		},
+	}, nil
+}