Ensure usage of names like 'Admin' are avoided for Azure SQL Server

Names like azure_superuser, azure_pg_admin, admin, administrator, root, guest, public for an Azure SQL Server Active Directory Administrator account are used, this may lead to unauthorized access via brute force attack.

In Azure Console -

1. Open the Azure Portal and go to SQL servers.
2. Choose the SQL server you wish to edit.
3. Under Overview, validate Server admin name is not predictable.
4. Select Save

In Terraform -

1. In the azurerm_sql_server resource, validate administrator_login name is not predictable.

References:
https://learn.microsoft.com/en-us/azure/azure-sql/database/logins-create-manage?view=azuresql
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/sql_server