Fixes a bug that was causing control panel edit fee pages to 404.
Adds an empty option for product option metas so that a meta value does not have to be selected.
Updates the edit product option flow to allow removing a meta option value.
Adds missing product meta events.
Renames the label for deleting an API key - for consistency with other control panel terminology.
Pluralizes the gateway metas relation property for consistency with the rest of the models.