Move cloud metadata packages and kubernetes resources marshaling to internal

Decouples cloud provider metadata packages from kubernetes related code

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

internal/cloud/azure/imds.go

@@ -0,0 +1,54 @@
+package azure
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+)
+
+// subset of azure imds API: https://docs.microsoft.com/en-us/azure/virtual-machines/windows/instance-metadata-service?tabs=linux
+// this is not yet available through the azure sdk (see https://github.com/Azure/azure-rest-api-specs/issues/4408)
+
+const (
+	imdsURL        = "http://169.254.169.254/metadata/instance"
+	imdsAPIVersion = "2021-02-01"
+)
+
+type imdsClient struct {
+	client *http.Client
+}
+
+// Retrieve retrieves instance metadata from the azure imds API.
+func (c *imdsClient) Retrieve(ctx context.Context) (metadataResponse, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", imdsURL, http.NoBody)
+	if err != nil {
+		return metadataResponse{}, err
+	}
+	req.Header.Add("Metadata", "True")
+	query := req.URL.Query()
+	query.Add("format", "json")
+	query.Add("api-version", imdsAPIVersion)
+	req.URL.RawQuery = query.Encode()
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return metadataResponse{}, err
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return metadataResponse{}, err
+	}
+	var res metadataResponse
+	if err := json.Unmarshal(body, &res); err != nil {
+		return metadataResponse{}, err
+	}
+	return res, nil
+}
+
+// metadataResponse contains metadataResponse with only the required values.
+type metadataResponse struct {
+	Compute struct {
+		ResourceID string `json:"resourceId,omitempty"`
+	} `json:"compute,omitempty"`
+}