fix(service_name): required to optional according to the doc

[TartanLeGrand]

Correct the service name according to the doc to use the var env in CI.

Exemple: https://registry.terraform.io/providers/ovh/ovh/latest/docs/resources/cloud_project_kube#service_name

[lpatte]

Hi

DefaultFunc is designed to work with required=true (doc). So you can not set service_name and set env var OVH_CLOUD_PROJECT_SERVICE and that work. The issue to change required by optional is that mean that the resource should work without service_name or env var OVH_CLOUD_PROJECT_SERVICE set and that not the case.

I think it's more a doc issue

[scraly]

I agree, the service_name (in attribute or in environment variable) is required, it's not optional.