Required checkboxes are not validated correctly on the server side

[jrauh01]

By default, in html you can't submit unchecked checkboxes if they are set to 'required'. In our forms, if you remove the 'required' tag in the browser's dev tools, you can submit a checkbox even if it's not checked. I think this shouldn't be possible to prevent submitting a form where the user's agreement is mandatory (terms and conditions for example).

[nilmerg]

Didn't verify this myself, but it seems that since a checkbox element always has a value, hasValue() always returns true. It is potentially enough to override it and return false in case the unchecked value is set.