Provide a way to connect to postgres DBs in private spaces using third-party clients (i.e. not `heroku pg:psql`)

[harto]

Do you want to request a feature or report a bug?

Feature

What is the current behavior?

It seems like the only way to query a database in a private space is via the pg:psql command. It would be nice to be able to use other tools (e.g. Postgres GUIs) to connect directly to the database. It looks like pg:psql sets up a local tunnel through a bastion host.

What is the expected behavior?

Ideally there would be a pg subcommand that would report the bastion host details, or that would create the ssh tunnel and report the local port number.