[#187] Fix handling ErrAccessDenied and ErrGatewayTimeout

If an Access Denied error occurs, we should
return 403 Forbidden instead of 400 Bad Request.
Gateway Timeout error we also need to process
and return the 504 Gateway Timeout code.

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

internal/service/frostfs/frostfs_test.go

@@ -0,0 +1,72 @@
+package frostfs
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/handler"
+	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+func TestHandleObjectError(t *testing.T) {
+	msg := "some msg"
+
+	t.Run("nil error", func(t *testing.T) {
+		err := handleObjectError(msg, nil)
+		require.Nil(t, err)
+	})
+
+	t.Run("simple access denied", func(t *testing.T) {
+		reason := "some reason"
+		inputErr := new(apistatus.ObjectAccessDenied)
+		inputErr.WriteReason(reason)
+
+		err := handleObjectError(msg, inputErr)
+		require.ErrorIs(t, err, handler.ErrAccessDenied)
+		require.Contains(t, err.Error(), reason)
+		require.Contains(t, err.Error(), msg)
+	})
+
+	t.Run("simple timeout", func(t *testing.T) {
+		inputErr := errors.New("timeout")
+
+		err := handleObjectError(msg, inputErr)
+		require.ErrorIs(t, err, handler.ErrGatewayTimeout)
+		require.Contains(t, err.Error(), inputErr.Error())
+		require.Contains(t, err.Error(), msg)
+	})
+
+	t.Run("deadline exceeded", func(t *testing.T) {
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond)
+		defer cancel()
+		<-ctx.Done()
+
+		err := handleObjectError(msg, ctx.Err())
+		require.ErrorIs(t, err, handler.ErrGatewayTimeout)
+		require.Contains(t, err.Error(), ctx.Err().Error())
+		require.Contains(t, err.Error(), msg)
+	})
+
+	t.Run("grpc deadline exceeded", func(t *testing.T) {
+		inputErr := fmt.Errorf("wrap grpc error: %w", status.Error(codes.DeadlineExceeded, "error"))
+
+		err := handleObjectError(msg, inputErr)
+		require.ErrorIs(t, err, handler.ErrGatewayTimeout)
+		require.Contains(t, err.Error(), err.Error())
+		require.Contains(t, err.Error(), msg)
+	})
+
+	t.Run("unknown error", func(t *testing.T) {
+		inputErr := errors.New("unknown error")
+
+		err := handleObjectError(msg, inputErr)
+		require.ErrorIs(t, err, inputErr)
+		require.Contains(t, err.Error(), msg)
+	})
+}