boolean fields should be settable as required (or not)

[tkimnguyen]

@davisagli was fixing this bug plone/plone.org#139 in plone.org with plone/plone.org#145 and we discussed how a customization to FormValidation.js was made for plone.org to allow requiring boolean fields.

Making this change in Volto would probably break some things so should be reserved for a major version upgrade.

This is a placeholder for discussion.

[davisagli]

"required" for a boolean field means several different things in different places:

1. In Zope schemas, a Bool field with required=True means that the field must be set to a boolean value (True or False) rather than None.
2. In JSON-Schema (which the Zope schema gets serialized to in the REST API) in general, required is a list of property names that must be present in the object (whether or not they are set to a value).
3. But volto makes a stronger interpretation of required in the JSON schema, and checks to make sure that the required properties are not empty.
4. plone.org's customization goes a step further (too far IMO) and interprets a required boolean field as meaning that the value must be True.

I think volto's current implementation is good and matches the backend interpretation of required pretty well.

If plone.org needs to enforce that a boolean field is checked, it's probably better to do that with a validator instead of required=True. Then the customization wouldn't be needed.