[#75962980] Check URL is blacklisted when reading from queue 

Check if a URL is blacklisted as we read it from the RabbitMQ queue to
prevent us from crawling blacklisted URLs.

Previously we would only check URLs that were extracted from a crawled
HTML document.
I'd like it to but not sure it's applicable here. Perhaps we could pair on it if you're in the office today?

`outbound` should never have a length greater than zero in this test, as the item published to the queue should be negatively acknowledged and never be sent on the `outbound` channel.