feat: implement login redirect middleware [BB-5090] [OSPR-6223]

[Cup0fCoffee]

Description

This PR implements new middleware that redirects all unathenticated users to login page. It enables admins to enable the middleware through settings for LMS to prevent unathenticated users from seeing any content.

Supporting information

BB-5090
OSPR-6223

Testing instructions

• Run make lms-up in the devstack
• Visit http://localhost:18000/courses/ (logout before that, if you're logged in) - you will be able to see the available courses
• Run make lms-shell in the devstack, open /edx/etc/lms.yml and under 'FEATURES' add ENABLE_REDIRECT_UNATHENTICATED_USERS_TO_LOGIN: true
• Exit the lms shell and run make lms-restart-devserver
• Now if you visit http://localhost:18000/courses/, you'll be redirected to login page
• If you log in, you should get redirected to the page you've tried to visit before logging in (in this case it's /courses/)
• You can try to repeat the last two steps with any page that doesn't usually require user to be authenticated, and you can add query string to the url, to check that it doesn't get lost after login

Other information

The middleware is implemented in the "new" style, i.e. without the use of MiddlewareMixin, to not introduce more things to refactor in the future. If there are reasons for why the MiddlewareMixin is preferred, I'll happily change the implementation to use it.

[openedx-webhooks]

Thanks for the pull request, @Cup0fCoffee! I've created OSPR-6223 to keep track of it in JIRA, where we prioritize reviews. Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
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Please let us know once your PR is ready for our review and all tests are green.

[natabene]

@Cup0fCoffee Thank you for your contribution. Is this ready for our review?

[edx-status-bot]

Your PR has finished running tests. There were no failures.

[Cup0fCoffee]

@natabene Yes.

[Cup0fCoffee]

@natabene, @0x29a has discovered that the current implementation of the feature breaks the third party authentication when enabled. We have a few ideas for how to fix it, and are working on it. However, we are not confident that our implementation can be comprehensive enough to be upstreamed.

If there is interest in the feature, we can discuss possible implementations and how to cover all corner cases on the forum in the future. For now this PR can be closed.

[openedx-webhooks]

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