fix(backend): secure production startup and migrations

backend/internal/testutil/postgres_integration.go

@@ -0,0 +1,68 @@
+//go:build integration
+
+// Package testutil contains opt-in helpers for isolated integration databases.
+package testutil
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"net/url"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+)
+
+// OpenIsolatedPostgres creates a random schema and binds every pooled test
+// connection to it through search_path. It never reads the production DSN.
+func OpenIsolatedPostgres(t testing.TB, config *gorm.Config) *gorm.DB {
+	t.Helper()
+	dsn := strings.TrimSpace(os.Getenv("TEST_DATABASE_URL"))
+	require.NotEmpty(t, dsn, "TEST_DATABASE_URL is required for integration tests and must point to an isolated database")
+
+	schema := randomSchemaName(t)
+	admin, err := gorm.Open(postgres.Open(dsn), config)
+	require.NoError(t, err)
+	adminSQL, err := admin.DB()
+	require.NoError(t, err)
+	require.NoError(t, admin.Exec(fmt.Sprintf(`CREATE SCHEMA "%s"`, schema)).Error)
+
+	schemaDSN, err := postgresSchemaDSN(dsn, schema)
+	require.NoError(t, err)
+	database, err := gorm.Open(postgres.Open(schemaDSN), config)
+	require.NoError(t, err)
+	isolationSQL, err := database.DB()
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		_ = isolationSQL.Close()
+		_ = admin.Exec(fmt.Sprintf(`DROP SCHEMA IF EXISTS "%s" CASCADE`, schema)).Error
+		_ = adminSQL.Close()
+	})
+	return database
+}
+
+func randomSchemaName(t testing.TB) string {
+	t.Helper()
+	value := make([]byte, 12)
+	_, err := rand.Read(value)
+	require.NoError(t, err)
+	return "senlin_test_" + hex.EncodeToString(value)
+}
+
+func postgresSchemaDSN(dsn, schema string) (string, error) {
+	if strings.Contains(dsn, "://") {
+		parsed, err := url.Parse(dsn)
+		if err != nil {
+			return "", err
+		}
+		query := parsed.Query()
+		query.Set("search_path", schema)
+		parsed.RawQuery = query.Encode()
+		return parsed.String(), nil
+	}
+	return strings.TrimSpace(dsn) + " search_path=" + schema, nil
+}