[html-formfu] RFC: i18n key changes

[Carl Franks]

The current default behaviour for Constraint errors is to search for
an i18n key of the form "form_${type}_error".

Unfortunately, this provides no means of disambiguating clashes
between errors from Constraints, Inflators, Validators and
Transformers.

For example both HTML::FormFu::Inflator::Imager and
HTML::FormFu::Transformer::Imager will both search for the i18n key
"form_imager_error".

I propose changing the key to the format: "form_${processor}_${type}"

Therefore the Imager examples above would become
"form_inflator_imager" and "form_transformer_imager", respectively.

To take an existing value as an example, "form_required_error" will
become "form_constraint_required".

The only code change that would be required would be changing the
default $form->auto_error_message() from "form_%t_error" to
"form_%s_%t".
This would obviously have an impact on anyone currently using non-core
i18Nnfile - however I feel it would allow us to provide a wider range
of i18n messages by default, rather than users having to write their
own.

Opinions?

If you can't tell - then yes, I'm trying to address anything now that
would break things, before making the non-dev CPAN release :)

Carl