Explore using DatabasePreparer when creating a database for integration tests

[wslulciuc]

Do we need our own PreparedDbRule? We're dynamically generating the config.yml, which I'm not a fan of (and something I think we can hopefully avoid). Looking at the src for PreparedDbRule, on instantiation, it's creating the DB connection based on the details contained in DatabasePreparer. Worth exploring that as an option.

[ashulmanWeWork]

Checked in a fix that gets us a cleaner solution (thanks @wslulciuc for the pointers). There is some more work we can do to make it even cleaner, but this will hopefully resolve the issue of intermittent test failures.

[wslulciuc]

Let's use JdbiRule instead to manage a Jdbi instance pointing to postgres.