Added access log to server and modified mock-fts to use it

cmd/mock-fts/main.go

@@ -23,7 +23,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"log"
 	"log/slog"
 	"net/http"
 	"os"
@@ -286,23 +285,17 @@ func run(ctx context.Context, opts *options) (err error) {
 	}()
 
 	// Serve the API.
-	out := os.Stdout
-	if opts.accessLogPath != "-" {
-		var logFile *os.File
-		logFile, err = os.OpenFile(
-			opts.accessLogPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o600,
-		)
-		if err != nil {
-			cancel()
-			<-workerDone
-			return fmt.Errorf("opening access log: %w", err)
-		}
-		defer func() {
-			err = errors.Join(err, logFile.Close())
-		}()
-		out = logFile
+	accessLogger, closeAccessLog, err := logging.OpenAccessLog(
+		opts.accessLogPath,
+	)
+	if err != nil {
+		cancel()
+		<-workerDone
+		return err
 	}
-	accessLogger := log.New(out, "", 0)
+	defer func() {
+		err = errors.Join(err, closeAccessLog())
+	}()
 
 	rateLimiter := mock.NewRateLimiter(opts.rateLimit, opts.rateWindow)
 	mux := http.NewServeMux()