Remove signup code

:bee: :bee: :bee: :bee: :bee: :bee: :bee: :bee: :bee: :bee: 

Do not deploy yet!

:bee: :bee: :bee: :bee: :bee: :bee: :bee: :bee: :bee: :bee: 

This branch removes the signup steps that have been moved to the signup app. It's ready for review but we'd like to wait at least a few days to confirm that the transition to the signup app is fully stable.