Postgres config management is now available!

@shaun, this is great! I’d love to be able to configure shared_preload_libraries and pg_stat_statements.track - here’s a related thread on the topic: pg_stat_statements extension in Postgres

I was able to do it with ssh + stolonctl as described in that thread, but I was definitely a little bit afraid of breaking things. A way to do it via flyctl would be awesome.