Is your feature request related to a problem? Please describe.
I find it annoying that i have to duplicate environmental settings or secrets, and i want to be able to daisy chain settings together and extend other environments

Describe the solution you'd like
If i have multiple environments described in my settings or secrets.yaml files, i want to be able to extend other envirnments, via a key or similar.

default:
  ..

development:
  key: ab

local:
  _extends: development
  env: local

here settings.local.key should be "ab"