sorry, took a bit longer than I wanted, but here it is. thanks for
looking into this! :) at first glance it seemed like it's more
straight-forward than I expected - but as always with JSONSchema.pm,
some rabbit-hole chasing later I am not quite so sure anymore. I hope my
walls of text below
Adds a third, optional parameter to register_format that allows specifying
a function that will be called after parsing and can validate the parsed
data. A validator should die on failed validation, and can also change the
parsed object by returning a modified version of it.
This is useful so one
