[FEATURE] Provide a way to verify and test templates in CI

[mteu]

Is your feature request related to a problem?

Writing a template for the Project Builder is rather easy. But with constantly evolving templates and an ever improving Project Builder who is to say that a template still works as expected?

Describe the solution you'd like

There should be a way to have templates be validated and tested against the Project Builder and against expected outcomes both locally and in the CI. That's why I'm proposing to come with such a feature.

Describe alternatives you've considered

Until now I've tested templates with the composer simulate manually. That's all good but it could be better.

Additional context

No response