Core Platform Team/Initiative/Adding Multiple Identity Providers to PluggableAuth/Initiative Vision

Vision: Support login from multiple identity providers in a single wiki
Stakeholder(s): Wiki admins who need to support authentication from off-wiki identity providers (e.g. admins of third-party Wikibase instances) Wiki users who wish to be able to login using existing credentials from other identity providers	Problem: (Admins) Configure wiki with one or more off-wiki identity providers (Admin) Configure username mapping for multiple providers (Users) Select identity provider on login	Solution: Add support for multiple authentication providers to PluggableAuth. Remove support for multiple authentication providers from OpenID Connect (support migration). Update core to support identity provider selection. (optional) Update core to better support passwordless identity providers. (optional)	Aligned Goals: Enhance Production Code Ownership, Support & Accountability for the Platform Engineering Team	Success Metrics: User is presented with a selection of identity providers to choose between and is able to successfully login to the wiki with any of them.