[management,misc] Fix configuration migration checks

The initial migration let an empty legacy Datadir override Management defaults and pulled Viper into WASM builds through the common util package.

Normalize the Management data directory, isolate template expansion from the loader dependency, and split source binding to satisfy the quality gate.

management/cmd/config.go

@@ -3,11 +3,19 @@ package cmd
 import (
 	nbconfig "github.com/netbirdio/netbird/management/internals/server/config"
 	configloader "github.com/netbirdio/netbird/util/config"
+	"github.com/netbirdio/netbird/util/envtemplate"
 )
 
 func loadManagementConfig(configPath string) (*nbconfig.Config, error) {
-	return configloader.Load(configPath, &nbconfig.Config{Datadir: defaultMgmtDataDir}, configloader.Options{
+	cfg, err := configloader.Load(configPath, &nbconfig.Config{Datadir: defaultMgmtDataDir}, configloader.Options{
 		TagName:   "json",
-		Transform: configloader.ExpandEnvTemplate,
+		Transform: envtemplate.Expand,
 	})
+	if err != nil {
+		return nil, err
+	}
+	if cfg.Datadir == "" {
+		cfg.Datadir = defaultMgmtDataDir
+	}
+	return cfg, nil
 }

management/cmd/config_test.go

@@ -10,6 +10,15 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestLoadManagementConfigUsesDefaultDataDirForEmptyValue(t *testing.T) {
+	configPath := filepath.Join(t.TempDir(), "management.json")
+	require.NoError(t, os.WriteFile(configPath, []byte(`{"Datadir":""}`), 0o600))
+
+	cfg, err := loadManagementConfig(configPath)
+	require.NoError(t, err)
+	assert.Equal(t, defaultMgmtDataDir, cfg.Datadir, "Empty legacy values should use the default data directory")
+}
+
 func TestLoadManagementConfigSources(t *testing.T) {
 	t.Setenv("MANAGEMENT_DATA_DIR", "/template-data")
 	t.Setenv("MANAGEMENT_ENCRYPTION_KEY", "template-key")