Override env variable by referencing itself

It can be useful when assigning value to an environnement / folder variable to reference itself.

For exemple, we can have an environment BASE_URL variable and in our User folder we may want to override BASE_URL variable to: BASE_URL/user

So in our request we can have as URL : BASE_URL/me instead of BASE_URL/user/me

When having a domain based application it can be very useful to avoid repetition and facilitate slug renaming.

Currently, we have an error if we try to recursively reference a variable: