Ensure public access is disabled for Azure IoT Hub

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. Go to Azure IoT Hub.
2. Choose an IoT Hub to edit.
3. In the Security settings, Choose Networking.
4. Click on the click on public access and choose disabled.
5. Click save.

In Terraform -

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

References:
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/iothub#public_network_access_enabled