I understand the idea of not mixing controller function for multiple
things. but I also think that having post urls, which cannot be get
(even they do have a sensible meaning) is not nice.

especially for the signup process, I would assume, that if you hit
enter in the url bar, you would loose all data in the form, but still
get to the same signup page.

therefore i added the token as part of the url and the post goes to
'/signup/:token'. when you get that url, you can restart signup
with the same token.