improve CLI configuration troubleshooting after updated

[hgiasac]

Check if environment variables are set and print instructions to developers. For example:

WARNING:

  * Headers forwarding should be enabled for the following authentication schemes: [cookie openIdConnect]
    See https://github.com/hasura/ndc-http/blob/main/docs/authentication.md#headers-forwarding for more information.

Environment Variables:
  Make sure that the following environment variables were added to your subgraph configuration:

  --- ./connector/docker.yaml
  services:
    app_myapi:
      environment:
        PET_STORE_API_KEY: $APP_MYAPI_PET_STORE_API_KEY
        # ...
  ---

  --- ./connector/connector.yaml
  envMapping:
    PET_STORE_API_KEY
      fromEnv: APP_MYAPI_PET_STORE_API_KEY
    PET_STORE_URL
      fromEnv: APP_MYAPI_PET_STORE_URL
    # ...
  ---

  --- .env
  APP_MYAPI_PET_STORE_API_KEY=
  APP_MYAPI_PET_STORE_URL=
  # ...
  ---

[github-actions]

Package	Line Rate	Health
github.com/hasura/ndc-http/connector	49%	➖
github.com/hasura/ndc-http/connector/internal	56%	➖
github.com/hasura/ndc-http/connector/internal/contenttype	64%	➖
github.com/hasura/ndc-http/connector/internal/security	55%	➖
github.com/hasura/ndc-http/ndc-http-schema/configuration	38%	❌
github.com/hasura/ndc-http/ndc-http-schema/openapi/internal	50%	➖
github.com/hasura/ndc-http/ndc-http-schema/openapi	40%	➖
github.com/hasura/ndc-http/ndc-http-schema/schema	32%	❌
github.com/hasura/ndc-http/ndc-http-schema/utils	44%	➖
Summary	49% (3785 / 7730)	➖

Minimum allowed line rate is 40%