Environment Groups

It would be nice to have environment groups. This would allow activating multiple environments at the same time.

Example: One environment group (Endpoints) would contain the API endpoint variable, and would have dev/test/live environments. Another group (Auths) could contain authentication API keys for different tenants (with a number of tenants for each env for instance). The environments would be tenant1/tenant2/tenant3. So, for any request I can specify Endpoints::dev, Auths::tenant2 as my active environments.

There is precedent here: RapidAPI (formerly Paw) has this feature, and is arguably the single most important feature (for me) that has kept me using that app across every other API client. Request chaining too, but I already see that in the roadmap :)