User Signup flow should start with email verification

[esteban-gs]

Wait for UX to confirm new UX flow:

In #378, we made the backend changes necessary to allow the signup flow to follow this order:

1. User signs up with email, first and last
2. User can use their login cookie to update their account

With this change, we can change the order of the signup flow in the UI.

Specifications:

• signup-citizen now only consists of a simple form with
  • first, last and email.
• The verify-email route can remain the same
• after login, we can check if any of these fields are filled out:
  • zip_code, interests
• If they aren't filled out, we can redirect the user to a finish-signup page that contains the other fields that are found in the current signup form. This form now can hit the PUT api/auth/users/{id} to update the user and the PUT api/auth/users/profile/:id endpoint to upload the profile image.