Prevent passing positional arguments to form fields

[Claude Paroz]

The documentation already indicates (**kwargs) for most of form field signatures. But in practice, this isn't enforced and any positional *args are passed to the __init__ methods.

I encountered a strange error with some code of mine which was due to some label passed erroneously as positional parameter:
distance = DecimalField("SomeLabel", max_digits=6, decimal_places=2) ("SomeLabel" was passed as max_value, which only crashed when validating the form with a strange comparison error).

I think that preventing positional parameters (with a lonely *) should avoid this sort of unexpected errors. This might however be backwards incompatible for previously well-functioning code.

[Tim Graham]

I think it's worth trying this -- we can always revert it and consider a deprecation path if prerelease testing indicates major pain. I don't recall encountering form fields using positional arguments during my time working with Django.

[Claude Paroz]

​PR

[GitHub <noreply@…>]

In 8e752d84:

Refs #28192 -- Made MultiValueField/ComboField fields argument required as documented.

[Claude Paroz <claude@…>]

In 54caca2:

Refs #28192 -- Fixed documentation of ChoiceField choices requirement

Thanks Tim Graham for noticing the issue.

[Claude Paroz <claude@…>]

In 81c3967e:

[1.11.x] Refs #28192 -- Fixed documentation of ChoiceField choices requirement

Thanks Tim Graham for noticing the issue.
Backport of 54caca2d34c7cb6807da0a82bcec7b3a679ac104 from master.

[Tim Graham <timograham@…>]

In 43b57400:

Fixed #28192 -- Required passing optional form field args as keyword args.