Using Project variables in `StackTemplates`

[kinseii]

What would you like to add The documentation says that we can use Project variables in other configuration objects:

variables - a set of data in yaml format that can be referenced in other configuration objects

However, the values from the Project are not filling in StackTemplates. Apparently they need to be passed to Stack first. So we would like to use the ability to pass variables from both Stack and Project in StackTemplates.