Confirm that validation fails if extra fields exist, add new test if not
I'm worried that the alerts validation may only fail if fields are missing, just because the gwcelery.tests.test_tasks_alert_validate
unit test is still passing on main after userguide!134 (merged) and userguide!138 (merged) were merged but before !967 (merged) is merged.
If the validation function doesn't flag extra fields, we need to write a new unit test in the test_tasks_alert_validate
module.