Usability (Authentication): Ideal methods to sign in? #6861

Context

Currently the user can login with Google and a Local User/Password (as well as Facebook in a temporary branch but this was mostly a proof of the recently proposed schema design in #6716).

Goal

We want to identify and prioritize alternative universal "Login with [Service]" buttons (pop-up based) to expand our single sign-on (SSO) options.

For example, platforms like Overleaf support ORCID and IEEE accounts to target academic users, while developer platforms heavily utilize GitHub or GitLab.

Scope & Technical Requirements

Protocol: Ideally supports standard OAuth 2.0 or OpenID Connect (OIDC).
(We can support other options, but it would require a bit more leg work to set up.)

Payload Requirements: The provider must expose endpoints to reliably retrieve:

1. A verified primary email address
2. The user's name
3. A permanent, unique user ID (sub claim)

Out of Scope (For Now):

Custom Enterprise, University, or Workplace SSO (SAML, Shibboleth, or tenant-specific Okta/Azure AD setups)

Questions for the team

What services make good potential options?