Allow setting environment variables for command tests

[kasimon]

Describe the feature: Add the ability to specify environment variables for command checks.

Describe the solution you'd like

command:
  vault status:
    exit-status: 0
    environment:
      VAULT_ADDR: "https://....:8200"
      VAULT_CACERT: "/etc/ssl/my-internal-ca.pem"
    timeout: 10000

Describe alternatives you've considered Create a wrapper script that sets the environment variables and is called by goss. Possible but not as elegant as if this feature was provided by goss itself.

[aelsabbahy]

Another way to do it today if you want to avoid a wrapper script is.

exec: "VAULT_ADDR=.. VAULT_CACERT=.. vault status"

That said, this sounds like a good enhancement to have, marking it as approved.