Make BooleanParser understand "on" as true

[apeiniger]

"on" is default value for checkboxes in html in many browsers, therefore it would be great if "on" would be treated as true as well in the BooleanParser.

[mpscholten]

Could be implemented like the YesNoBooleanParser

[yuvalherziger]

Good point, that is indeed a missing feature, we can implement a type parser for that

[yuvalherziger]

@apeiniger @mpscholten I'm not sure because it's been a while, but on for a default checkbox button always returns "on" if the checkbox exists, see example here. The point is, adding an OnOffBooleanParser is technically possible, but is it of any added value?

PR #47 already supports it, but the question at hand is whether in terms of HTML (of which the request parser is agnostic) a form would ever submit an off value by default for any browser

[apeiniger]

Yeah, that was my idea as well, that's why I thought it could maybe be added to the normal BooleanParser instead, but up for discussion.