Convert to OAuth2 login provider instead of OIDC

[bradenmacdonald]

This changes our use of auth-backends from the deprecated OIDC provider to the OAuth2 provider, because I rebuilt my devstack and the OIDC one wasn't working.

This is working, however there are a couple issues:

• Superuser permission doesn't seem to be applied via SSO - when I login as a user who has staff and superuser permissions, the blockstore user only has staff permission
  • perhaps related to this but I think I had that fix?
• The OAuth2 backend by default requests the user_id scope, and based on these two PRs, that should work, but the default devstack LMS is giving me an invalid_scope error when user_id is included. Not sure why.

Test instructions: See the instructions added to the README.

[ormsbee]

I don't know the answer to your questions, but I'm definitely happy to merge this as is and worry about those issues later.

[bradenmacdonald]

Thanks @ormsbee!

[bradenmacdonald]

@robrap Would you happen to know the default devstack LMS is giving an invalid_scope error when our IDA tries to use the OAuth2 SSO flow and requests the user_id scope from the LMS? (i.e. why edx-auth-backends does not work out of the box, unless I override it to not request that scope?)

I'm guessing it relates to https://github.com/edx/auth-backends/pull/59 and https://github.com/edx/edx-platform/pull/20057 but I definitely have both of those PRs merged in the branches I'm using for edx-auth-backends and for the LMS.

[robrap]

I forwarded an email that should help. Let me know if you still have problems.

[robrap]

FYI: @nasthagiri: another instance of trouble for someone unless and until we swap the default scopes.

[bradenmacdonald]

Ah, thanks so much @robrap :) That was the missing info I needed. Everything is working well now.

[openedx-webhooks]

Although this pull request is already merged, I've created OSPR-5450 so that we can track it in Jira.

There is nothing you have to do. No action is needed from your side. Thanks again for your contribution.