Ensure user id's are all system managed for Azure Container Group

Azure Container Group identities can be managed by Azure so that there is not a lack of accountability with regards to user activity. To learn more about managed identities, see the Azure documentation.
References:
https://learn.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/overview

Microsoft has provided detailed guidance on how to create and use Managed Identities with Active Directory for launching Container Instances. To learn how to create the appropriate prerequisites, then launch the services you require, see the Azure documentation below. Once the identity prerequisites are configured, you can also use Terraform.

In Terraform -

1. In the azurerm_container_group resource, create an identity block.
2. Set the type to SystemAssigned and add a list of identity_ids as needed.

References:
https://learn.microsoft.com/en-us/azure/container-instances/container-instances-managed-identity
https://learn.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/overview
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/container_group#identity