As noticed by Yuya, when I changed the function (during review) to
work with underscore-separated names as input, I forgot to make sure
the returned name was also underscore-separated. We don't have any
cases where it matters yet, but it should still clearly be fixed.
Instead of converting the hyphen-separated value we already have in
previous, I'm changing it so we convert to the underscore-separated
values to be hyphen-separated only when we need to display them. This
will also help a coming change where we allow the inputs to native
strings instead only bytes.