config data provided via API to hooks or commands with unknown fields are accepted and silently ignored

example data:

{"command": "class-add", "arguments": {"client-classes": [{"name": "ipxe", "unknown": "123"}]}

In that case "unknown" field is accepted and silently ignored. Kea should raise an error that data violates a schema, ie. expected format. Otherwise in case of e.g. a typo it may be annoying that expected behavior is not observed while no error is returned.