Option Group ID attributes do not strip spaces

[jacksonhyde]

Currently the id attribute value for many elements is derived from the value of the field or field option. Without any formatting it is possible for an ID to contain spaces (and presumably other non-spec characters).

You can see this in action on the Electronic Visa Waiver form flow:

This does violate the HTML spec, but a more pragmatic issue is that it prevents the label being associated with the button in the NVDA screenreader.

Perhaps we could add an id attribute to the options objects created in lib/template-mixins.js which stripped out illegal chars and formatted to an appropriate case (kebab case)?

This may be an issue with other elements, but so far we've only had issues with option groups.