Enable fetching of last request from HttpMockServer

Sometimes in my tests, I want to make looser assertions over the requests being made to the {{HttpMockServer}}. As such, I'd find it useful to be able to ask the {{HttpMockServer}} for the last request it received. Then I can make more granular assertions over the last request, rather than just calling {{verify()}}.

I've added a test, let me know what you think.