Activating statiegeld_tokens will limit the use of the statiegeld plugin
for container deposit refunds to what was bought at this venue.
Still needs documentation.
Changes to 'statiegeld' and 'undo' were made to support the new
plugin, specifically:
- metadata (attributes) added in $cart->add, for the statiegeld_tokens
plugin to use.
- statiegeld plugin now shares a global variable (configuration).
- undo can now be rolled back during hook_checkout.
