Adding a `post_handler` on a `Table` action creates a button that doesn't do anything when clicked

[boxed]

confirm_slots = Table(
        title=gettext('Confirm planning changes'),
        auto__model=Slot,
        actions__confirm=Action.button(
            post_handler=confirm_slots__post_handler,
        ),
    )

The reason nothing happens is because the <button> will end up in the html without a surrounding <form>, which means there is nothing to submit.

I think we should have an error or warning for this. I found it surprising.