[Bug]: Connections to the database cannot be closed

[innocenzi]

In PHP, we cannot manually close a PDO connection. All references to the PDO instance must be garbage-collected in order to close the connection.

Internally, Tempest passes the PDO object around in multiple classes (Database, TransactionManager and PdoInitializer). We would need to wrap it so we can close connections manually.

[blackshadev]

I am unsure if the label "bug" is applicable. But I created a PR which should help your efforts in #857 .