i want to pass in environment variables into `meltano.yml`something like this:
- name: tap-postgres
        config:
          host: localhost
          user: ${PGUSER}
          port: ${PGPORT}
          password: ${PGPASSWORD}
          database: ${PGDATABASE}
i can confirm that these env variables are set when i run 
env
, but when i run 
meltano config tap-postgres test
 it doesn't appear to have set these values:
File "/meltano-project/.meltano/extractors/tap-postgres/venv/lib/pionError: Need either the sqlalchemy_url to be set or host, port, user, and password to be set
is there something else i can do to determine why these variables are not getting set? in general, im finding it difficult to debug and understand what meltano is doing under the hood when i get into situations like these