Add Ruby 3.2 to the CI matrix

[petergoldstein]

In addition to adding Ruby 3.2 to the CI matrix, I updated the version of the checkout action.

To get the specs to green I had to make a few additional changes:

1. Add explicit hashes in the with clauses to remove ambiguity with keyword arguments
2. Update the safeguard logic to treat an empty string for host as local.

This runs green on my fork.