Dynamic environment variables

[RobinSchmid7]

Description

I would be very useful to be able to set dynamic environment variables in the env_file. The work around seems to be currently to run a bash script that loads these parameters before running docker compose. It would be much cleaner if the env_file could directly load these parameters.

E.g.

services:
  webapp:
    env_file: params.env

where param.env contains

DYN_PARAM=${SOME_OTHER_PARAM}

[ndeloof]

This is already how things happen:

$ SOME_OTHER_PARAM=test docker compose config
services:
  webapp:
    environment:
      DYN_PARAM: test