Using connection string with `target_session_attrs`

[nickpoorman]

I'm curious if anyone has tried using target_session_attrs with this. PostgreSQL and libpq both seem to support it. https://github.com/ged/ruby-pg/blob/5db4b5523a153f38697157f1775d90b7218f9c25/spec/pg/connection_spec.rb#L397

Background: https://www.cybertec-postgresql.com/en/new-target_session_attrs-settings-for-high-availability-and-scaling-in-postgresql-v14/