Revert "Fix authentication for OpenID users."

SSO will be implemented using SAML in the future instead.

This reverts commit 206e7644a5be926157579549964cfe5bbb5bda65.
Revert "Don't use internal_password to authenticate when using OpenID SSO."

SSO will be implemented using SAML in the future.

This reverts commit 32b58c87c8023c043272f44685b845ad175a7c98.
Revert "Implement SSO using OpenID."

SSO will be implemented using SAML in the future.

This reverts commit c17bd29b200b31945bba09633d17df5848c5bf34.