Ensure a firewall is attached to Azure SQL Server

Azure SQL Server does not have a firewall rule associated, this may make it too vulnerable.

In Azure Console -

1. Open the Azure Portal and go to SQL servers.
2. Choose the SQL server you wish to edit.
3. Under Networking, set Firewall rules.
4. Select Save

In Terraform -

1. In the azurerm_sql_firewall_rule resource, set name, resource_group_name, server_name, start_ip_address and end_ip_address.

References:
https://learn.microsoft.com/en-us/azure/azure-sql/database/firewall-configure?view=azuresql
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/sql_firewall_rule