pgBouncer is being added to PgOSM Flex! This should help the connection load with --append workloads

It is a WIP but I *think* it is functional! Testing and feedback welcome.

This finally became possible b/c pgBouncer added support for prepared statements 🤓

#pgosm #postgis #openstreetmap #gischat

https://github.com/rustprooflabs/pgosm-flex/pull/243