Users app + signup/login pages

[reedlauber]

This is step 1 of getting the frontend (React) app to be able to talk to the API (Django) app. We need to be able to create new users, let them log in, and be able to persist an authentication token to be used for subsequent API requests.

users app

First, this adds a new Django "app" called users that is intended to centralize all the logic needed around user management.

• The User model was moved from the transactions app in to users
• A register View and endpoint were added
• A me View was added so that the client can check if a session is active and a token can fetched if needed
• Login is provided by rest_framework

Auth pages

• New "Sign up" and "Log in" pages were added
• Form styling CSS
• Logic to store auth tokens in browser SessionStore, and include in API request headers

More logic to request and display transactions will be included in a followup PR.

[brukeg]

+1 Thank you for the in person explanation.