Log out user from all devices

[rgraber]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

Adds a new endpoint that will log the calling user out of all sessions and devices.

Notes

Adds usersessions app from allauth, which keeps track of sessions by user using UserSession objects created by a middleware class.

Adds a new endpoint that looks for all UserSession objects associated with the calling user and uses the usersessions adapter to delete all the associated sessions.

To test, login in separate browsers (or the same browser with private windows). curl the new /logout-all endpoint. Refresh the page in all browsers and you should be taken to the login page.

[notion-workspace]

Endpoint to log out on all devices