[FEATURE] Allow/Deny Customized Restrictions

[syepes]

Summary

Having the possibility to customized the allowed deployments would be a great addition and would be very complementary to the custom layering feature.

Motivation

Once we start using the custom layering, the default deployments restrictions start to not really match the new layering and deployment granularity.

Guide-level explanation

It would be great to have a generic or simpler way of restricting the deployments only when certain of the Environment Variables have the allowed values.

class AllowCustom
class DenyCustom

This could be similar to the way we define custom layers.