Up for debate, but part of me prefers having this connection and channel creation and closing happening within the `MBCRegistrationEmailController`. The connection and channel are being created here explicitly for this MBC alone. So this code at the bottom could instead become something like...

```
$mbc = new MBCRegistrationEmailController($credentials, $config);
$mbc->subscribeToMailChimp();
```

And then the destructor can take care of closing the channel and connection.