Implement an environment variable validation system #42
Description
So we can define having to use specific environment variables in an application, but we should have some utility that allows to inspect required environment variables. If any of those would be missing from a setup, then we could stop the application from booting until that's fixed.
We could set this module as optional as this shouldn't stop developers from building their applications but this is definitely something to consider to ensure that all configurable content is present when booting an application.