Lifecycle: shutdown connection pool

[pierre]

See https://github.com/brettwooldridge/HikariCP/wiki/FAQ:

Q: How do I properly shutdown the HikariCP DataSource?

A: Shutting down the DataSource is especially important in web application containers
where applications can be hot-deployed. Call the shutdown() or close() method on
the HikariDataSource instance. You can typically configure Spring or other IOC containers
to specify a "destroy" method.