Both in the 'schema modal page' and in the 'resource modal page', the field
indicating whether a value is mandatory, is rendered as a text input.
Users have to literally type 'true' or 'false', which is rather unusal for
a HTML view (even though 1 of the two cases even has an autocomplete...)
The attached patch changes both fields to be checkboxes (and changes some
labels to better depict the intention of the fields)