Maint: internal/storage rework

- No more global variables
- Inject merged servers to configuration package
- Fix #566: configuration parsing to use persisted servers.json
- Move server data files from `internal/constants` to `internal/storage`

internal/constants/cyberghost_test.go

@@ -3,16 +3,29 @@ package constants
 import (
 	"testing"
 
+	"github.com/golang/mock/gomock"
+	"github.com/qdm12/gluetun/internal/storage"
+	"github.com/qdm12/golibs/logging/mock_logging"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func Test_CyberghostGroupChoices(t *testing.T) {
 	t.Parallel()
+	ctrl := gomock.NewController(t)
+
+	logger := mock_logging.NewMockLogger(ctrl)
+	logger.EXPECT().Info(gomock.Any())
+
+	storage, err := storage.New(logger, "")
+	require.NoError(t, err)
+
+	servers := storage.GetServers()
 
 	expected := []string{"Premium TCP Asia", "Premium TCP Europe",
 		"Premium TCP USA", "Premium UDP Asia", "Premium UDP Europe",
 		"Premium UDP USA"}
-	choices := CyberghostGroupChoices()
+	choices := CyberghostGroupChoices(servers.GetCyberghost())
 
 	assert.Equal(t, expected, choices)
 }