Django login and logout functionality

[Archmonger]

Description

This PR contains any hooks and settings needed to make user authentication in Django easy.

This PR exists because Django's requires cookies to retain login status. ReactPy is rendered via WebSockets, and browsers do not allow active WebSocket connections to create/modify cookies.

To work around this limitation, when reactpy_django.hooks.use_auth().login() is called within your application, ReactPy will automatically create a login token and command the browser to fetch it at our new HTTP endpoint.

• fix login / logout functions #204

Changelog

• User login/logout features!
  • reactpy_django.hooks.use_auth to provide persistent login and logout functionality to your components.
  • settings.py:REACTPY_AUTH_TOKEN_TIMEOUT to control the maximum seconds before ReactPy no longer allows the browser to obtain a persistent login cookie.
  • settings.py:REACTPY_CLEAN_AUTH_TOKENS to control whether ReactPy should clean up expired authentication tokens during automatic cleanups.
• The ReactPy component tree can now be forcibly re-rendered via the new reactpy_django.hooks.use_rerender hook.

Checklist

Please update this checklist as you complete each item:

• Tests have been developed for bug fixes or new functionality.
• The changelog has been updated, if necessary.
• Documentation has been updated, if necessary.
• GitHub Issues closed by this PR have been linked.

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