Add a preview option for signup status mailer...

Issue Summary

At the moment, there is no easy way to test the emails sent out by the signup status mailer (to see how they look, test that the tokens say what you expect, etc...). AFAIK, the only thing to do is to register for the event, and then set your status to trigger each email, which is kind of a hassle.

I have no idea how complicated this would be to implement, but it seems like it could be possible to add a button that either produces a text field with all the emails, one after the other, or sends a copy of all the emails to the node author.

Either would be very valuable.