Add JWT token refresh endpoint

[khvn26]

1. Expose rest_framework_simplejwt.views.TokenRefreshView. Subclass it so it sets an cookie in lieu with current auth views (see authorise_response for implementation).
2. Extend authorise_response to set both access and refresh tokens.
3. We'll probably need to change the SIMPLE_JWT["AUTH_TOKEN_CLASSES"] setting and switch from SlidingToken to AccessToken.
4. Make the default token lifetime significantly shorter, as they won't be invalidated anymore.
5. Refresh tokens should be invalidated on logout and password change.

Refer to simplejwt documentation in order to perform the above.