`NGINX.NGINXPLUS/stable/2022-08-01` - define SKU names as Enum

[wuxu92]

Can the name of nginx deployments SKU defined as Enum values, so it can be generated in SDK and easy to use?

related swagger: https://github.com/Azure/azure-rest-api-specs/blob/1d9c9c68844d2b5883621069d5bf0c958841782f/specification/nginx/resource-manager/NGINX.NGINXPLUS/stable/2022-08-01/swagger.json#L1059

[tombuildsstuff]

ping @ruowan @JackTn any idea of a timeline for this one?

[ryepup]

I'd like to close this issue based on https://github.com/hashicorp/terraform-provider-azurerm/pull/25400. These skus map to azure marketplace plan names, and we use the private plan feature to make customized plan names that are not available to the public.