Ensure audit log retention period is greater than 90 days for Azure PostgreSQL Server

Audit log retention period is not set to at least 90 days for Azure PostgreSQL Server, this may make audit challenging.

In Azure Console -

1. Open the Azure Portal and go to Azure Database for PostgreSQL servers.
2. Choose the PostgreSQL server you wish to edit.
3. Under Server parameters, set retention_period_in_days greater than 90 days.
4. Select save.

In Terraform -

1. In the azurerm_postgresql_configuration resource, set retention_days greater than 90 days.

References:
https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/quickstart-create-server-portal
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/postgresql_server#retention_days