Post-Login signup page(s)

[connorlbark]

Description

After the user logs in & their credentials are on-device, we need to redirect to a form where we can grab more information about the user. At the very least, we need a username.

Since this is the first ticket which hits REST API endpoints, we should also make the process of making API calls streamlined / generic.

Dependents

Depends on: #1

Spec

• Redirects after logging in to a signup page iff no account has been created.
• If the user already has an associated account, either log them in directly (if we decide only one account per email) or let them select which account to log into with a simple view
• Form hits the signup endpoint & goes to profile if successful.
• If unsuccessful, displays error. If there is a way to make like an error banner generically for all rest api calls, this is probably a good time to do it