feat: env vars warning on invalid values

[miton18]

With the introduction of "?check=true" on PUT on app environment.

This PR emit warnings on invalid env values but still accept the configuration.

This is a first step, for the next one:

• shoud we return an error on invalid values and return ?
• can we have a version of this feature which validate only ?
• can we implement validation on a more integrated version with TF attribute validation ?