bootstrap: default to format=cloud-config (#355)

* bootstrap: default to `format=cloud-config`

Not every bootstrap provider sets the `format` key and i wasn't able to find any requirement for it in the capi contract.

With this change we default to cloud-config, as it was without this check, to restore functionality with other non-kubeadm bootstrap providers.

Takes care of cases where the CAPMOX controller errored out with
```
err="failed to reconcile VM: error retrieving format data: secret `format` key is missing"
```

* make the linter happy

internal/service/vmservice/bootstrap.go

@@ -158,11 +158,12 @@ func getBootstrapData(ctx context.Context, scope *scope.MachineScope) ([]byte, *
 		return nil, nil, errors.Wrapf(err, "failed to retrieve bootstrap data secret")
 	}
 
+	format := cloudinit.FormatCloudConfig
 	f, ok := secret.Data["format"]
-	if !ok {
-		return nil, nil, errors.New("error retrieving format data: secret `format` key is missing")
+	if ok {
+		format = string(f)
 	}
-	format := string(f)
+
 	value, ok := secret.Data["value"]
 	if !ok {
 		return nil, nil, errors.New("error retrieving bootstrap data: secret `value` key is missing")

internal/service/vmservice/bootstrap_test.go

@@ -169,21 +169,29 @@ func TestGetBootstrapData_MissingSecretValue(t *testing.T) {
 	}
 	require.NoError(t, client.Create(context.Background(), secret))
 
-	data, format, err := getBootstrapData(context.Background(), machineScope)
+	// missing value
+	data, _, err := getBootstrapData(context.Background(), machineScope)
 	require.Error(t, err)
-	require.Equal(t, err.Error(), "error retrieving format data: secret `format` key is missing")
+	require.Equal(t, "error retrieving bootstrap data: secret `value` key is missing", err.Error())
 	require.Nil(t, data)
-	require.Nil(t, format)
 
-	// missing value
-	secret.Data["format"] = []byte("cloud-config")
+	secret.Data["value"] = []byte("notdata")
+	require.NoError(t, client.Update(context.Background(), secret))
+
+	// test defaulting of format to cloud-config
+	data, format, err := getBootstrapData(context.Background(), machineScope)
+	require.Equal(t, cloudinit.FormatCloudConfig, ptr.Deref(format, ""))
+	require.Equal(t, []byte("notdata"), data)
+	require.Nil(t, err)
+
+	// test explicitly setting format to ignition
+	secret.Data["format"] = []byte(ignition.FormatIgnition)
 	require.NoError(t, client.Update(context.Background(), secret))
 
 	data, format, err = getBootstrapData(context.Background(), machineScope)
-	require.Error(t, err)
-	require.Equal(t, err.Error(), "error retrieving bootstrap data: secret `value` key is missing")
-	require.Nil(t, data)
-	require.Nil(t, format)
+	require.Equal(t, ignition.FormatIgnition, ptr.Deref(format, ""))
+	require.Equal(t, []byte("notdata"), data)
+	require.Nil(t, err)
 }
 
 func TestGetNetworkConfigDataForDevice_MissingIPAddress(t *testing.T) {