[html-formfu] model-dbic update - nested_base accessors

[Carl Franks]

I've committed some changes to HTML-FormFu-Model-DBIC which allow you
to define a Block, that uses nested_base to point to a ResultSource
accessor which isn't a column or relationship.

For example, in my 'Groups' result-source, I have a column1 method, like so:

    sub column1 {
        my ($self) = @_;

        my $content = $self->find_or_new_related( 'content', { region
=> 'column1' } );

        if ( @_ > 1 ) {
            $content->update(@_);
        }

        return $content;
    }

This allows me to do
    $group->column1;
instead of
    $group->find_related( 'content', { region => 'column1' } );

In my group-editing form, I can now do this:

    ---
    elements:
      - name: group_name

      - type: Block
        nested_name: column1
        model_config:
          nested_base: column1

        elements:
          - name: content

So now, both default_values() and update() will use the Block to
follow the related-row, and get/set the 'content' value from that row.

The reason I've added this, is to be able to more flexibly handle
'has_many' relationships, without having to use a Repeatable block.
Hope it might be useful for someone else too...

Cheers,
Carl