Ensure public network access disabled for Azure Eventgrid Domain

Allowing unrestricted, public access to cloud services could open an application up to external attack. Disallowing this access is typically considered best practice.

In Azure Console -

1. Open the Azure Portal and go to Event Grid Domains.
2. Select the Event Grid Domain you wish to edit.
3. Under Settings, choose Networking.
4. On the Public access tab, set Allow Access From to Private endpoints only.
5. Configure the Private Endpoint tab as needed.

In Terraform -

1. In the azurerm_eventgrid_domain resource, set public_network_access_enabled to false.

References:
https://learn.microsoft.com/en-us/azure/event-grid/
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/eventgrid_domain