attestation: add option for MAA fallback to verify azure's snp-sev id key digest (#1257)

* Convert enforceIDKeyDigest setting to enum

* Use MAA fallback in Azure SNP attestation

* Only create MAA provider if MAA fallback is enabled

---------

Signed-off-by: Daniel Weiße <dw@edgeless.systems>
Co-authored-by: Thomas Tendyck <tt@edgeless.systems>

internal/cloud/azure/logger.go

@@ -31,7 +31,7 @@ func NewLogger(ctx context.Context) (*Logger, error) {
 	if err != nil {
 		return nil, fmt.Errorf("loading credentials: %w", err)
 	}
-	imdsAPI := &imdsClient{
+	imdsAPI := &IMDSClient{
 		client: &http.Client{Transport: &http.Transport{Proxy: nil}},
 	}
 	subscriptionID, err := imdsAPI.subscriptionID(ctx)