craft\commerce\services\Formulas enhance Twig environment

[Anubarak]

Could you please allow users to add custom functions here?

Our client needs to add special checks if the user has not a certain group and special field layouts but currently you don't even pass the entire order object in your _isDiscountConditionFormulaValid function
Not sure what the purpose is, but order.customer is not defined and you can't even fetch the customer because craft is not available in your Twig environment.

So please provide a way to enhance your private environment to add custom functions at least so we can call PHPCode in some way.