feat: add Go migration compatibility foundation

backend/internal/postgres/open.go

@@ -0,0 +1,75 @@
+package postgres
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+type Module struct {
+	pool  Pool
+	Store *Store
+}
+
+func (module *Module) Close() {
+	if module != nil && module.pool != nil {
+		module.pool.Close()
+	}
+}
+
+func Open(ctx context.Context, config Config) (*Module, error) {
+	if config.Backend == BackendLocal {
+		return &Module{Store: NewDatabase(config, nil)}, nil
+	}
+	if config.Backend != BackendPostgres {
+		return nil, fmt.Errorf("unsupported data backend %q", config.Backend)
+	}
+	poolConfig, err := pgxpool.ParseConfig(config.DatabaseURL)
+	if err != nil {
+		return nil, fmt.Errorf("parse DATABASE_URL: %w", err)
+	}
+	poolConfig.MaxConns = config.PoolMax
+	poolConfig.MaxConnIdleTime = config.IdleTimeout
+	poolConfig.ConnConfig.ConnectTimeout = config.ConnectionTimeout
+	poolConfig.ConnConfig.RuntimeParams["statement_timeout"] = strconv.FormatInt(config.StatementTimeout.Milliseconds(), 10)
+	poolConfig.ConnConfig.RuntimeParams["application_name"] = config.ApplicationName
+	switch config.SSLMode {
+	case SSLDisable:
+		poolConfig.ConnConfig.TLSConfig = nil
+		poolConfig.ConnConfig.Fallbacks = nil
+	case SSLVerifyFull:
+		if config.TLSConfig == nil {
+			return nil, fmt.Errorf("TLS configuration is required when DATABASE_SSL_MODE=verify-full")
+		}
+		tlsConfig := config.TLSConfig.Clone()
+		if tlsConfig.ServerName == "" {
+			tlsConfig.ServerName = poolConfig.ConnConfig.Host
+		}
+		poolConfig.ConnConfig.TLSConfig = tlsConfig
+		poolConfig.ConnConfig.Fallbacks = nil
+	default:
+		return nil, fmt.Errorf("unsupported DATABASE_SSL_MODE %q", config.SSLMode)
+	}
+	pool, err := pgxpool.NewWithConfig(ctx, poolConfig)
+	if err != nil {
+		return nil, fmt.Errorf("open PostgreSQL pool: %w", err)
+	}
+	adapter := &pgxPoolAdapter{pool: pool}
+	return &Module{pool: adapter, Store: NewDatabase(config, adapter)}, nil
+}
+
+type pgxPoolAdapter struct {
+	pool *pgxpool.Pool
+}
+
+func (p *pgxPoolAdapter) Query(ctx context.Context, sql string, args ...any) (Rows, error) {
+	return p.pool.Query(ctx, sql, args...)
+}
+
+func (p *pgxPoolAdapter) Close() {
+	p.pool.Close()
+}
+
+var _ Pool = (*pgxPoolAdapter)(nil)