[Maypole] edit by unique field

[Kevin Connor]

out-of-the-box Maypole provides edit functionality using a numeric
primary key in the url:

beerdb/beer/edit/1

I'd like to support url's of the following form:

beerdb/beer/edit/amberlight

(presuming amberlight is the value for a unique field)

I'm thinking along REST principles.  It should bring up the add new page
if the value doesn't exist.

Anyway, it seems like to do it would mean overriding $class->retrieve.

see the call to
     my $obj = $class->retrieve( $r->{args}->[0] );
within
     Maypole::Model::Base::process

Thoughts?  Is this documented somewhere I've missed?

-Kevin Connor