Page field checkbox value not saved

[onionradish]

Adding a checkbox field foo to a page blueprint does not correctly save/update the value. It's always '0' or false.

form:
    fields:
        header.foo:
            type: checkbox
            label: foo
            name: foo
            title: foo
            validate:
                type: bool

Results in the header value always equal to false, regardless of whether checked/saved or unchecked/saved. Same field with type: toggle works correctly.

[onionradish]

It's possible that part of the issue is in typeCheckbox() in Grav\Common\Data\Validation.php - the test there is unlike others.