feat(caldav): import caldav categories as Labels (#1413)

Resolves #1274

Co-authored-by: ce72 <christoph.ernst72@googlemail.com>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/1413
Reviewed-by: konrad <k@knt.li>
Co-authored-by: cernst <ce72@noreply.kolaente.de>
Co-committed-by: cernst <ce72@noreply.kolaente.de>

pkg/user/user_test.go

@@ -386,7 +386,7 @@ func TestListUsers(t *testing.T) {
 
 		all, err := ListAllUsers(s)
 		assert.NoError(t, err)
-		assert.Len(t, all, 14)
+		assert.Len(t, all, 15)
 	})
 	t.Run("no search term", func(t *testing.T) {
 		db.LoadAndAssertFixtures(t)