This was broken in #8801 when abstracting code shared with OIDC.
After this change both SAML and OIDC have a concept of
grandfathering users, but with different implementations.
Checks that the localpart returned by mapping providers for SAML and
OIDC are valid before registering new users.
Extends the OIDC tests for existing users and invalid data.
Co-authored-by: Benjamin Koch <bbbsnowball@gmail.com>
This adds configuration flags that will match a user to pre-existing users
when logging in via OpenID Connect. This is useful when switching to
an existing SSO system.
