[release-11.4.2] AuthN: Refetch user on "ErrUserAlreadyExists" (#100585)

* AuthN: Refetch user on "ErrUserAlreadyExists" (#100346)

* AuthN: Refetch user on "ErrUserAlreadyExists"

(cherry picked from commit 0b4c622df8)

* Fix test

pkg/services/authn/authnimpl/sync/user_sync_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/grafana/authlib/claims"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
 
 	"github.com/grafana/grafana/pkg/infra/tracing"
@@ -447,6 +448,34 @@ func TestUserSync_SyncUserHook(t *testing.T) {
 	}
 }
 
+func TestUserSync_SyncUserRetryFetch(t *testing.T) {
+	userSrv := usertest.NewMockService(t)
+	userSrv.On("GetByEmail", mock.Anything, mock.Anything).Return(nil, user.ErrUserNotFound).Once()
+	userSrv.On("Create", mock.Anything, mock.Anything).Return(nil, user.ErrUserAlreadyExists).Once()
+	userSrv.On("GetByEmail", mock.Anything, mock.Anything).Return(&user.User{ID: 1}, nil).Once()
+
+	s := ProvideUserSync(
+		userSrv,
+		authinfoimpl.ProvideOSSUserProtectionService(),
+		&authinfotest.FakeService{},
+		&quotatest.FakeQuotaService{},
+		tracing.NewNoopTracerService(),
+	)
+
+	email := "test@test.com"
+
+	err := s.SyncUserHook(context.Background(), &authn.Identity{
+		ClientParams: authn.ClientParams{
+			SyncUser:    true,
+			AllowSignUp: true,
+			LookUpParams: login.UserLookupParams{
+				Email: &email,
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+}
+
 func TestUserSync_FetchSyncedUserHook(t *testing.T) {
 	type testCase struct {
 		desc        string