I really like the addition of this class :+1: though I'm not sure I'm in favor of the name of this method for a couple reasons:

1. `run!` doesn't really indicate that we're creating a friendship between two users and delivering an email.
2. By convention, bangs (!) should only be used when there is a corresponding non-bang method. So, in order to appropriately name a method `run!`, we would also need a `run` method. We can talk about this in depth at a later point.