identity_domain = service instance ID or identity service ID?

[kumar-dhanagopal]

In https://www.terraform.io/docs/providers/opc/index.html, the current description of "identity_domain" is: "(Optional) The Identity Domain name (for Traditional accounts) or Identity Service ID (for IDCS accounts) of the environment to use. It can also be sourced from the OPC_IDENTITY_DOMAIN environment variable."

When I tested against a production OPC account, the 'terraform apply' command failed if I specified the identity service ID. The command worked fine when I specified the service instance ID.