Spec 12 S2: openid-client 6.8 (decision 0004). Discovery, PKCE + state + nonce, ID token
signatures checked, userinfo always read. Users connect their OpenID account from My account
and sign in either way; no accounts are made; a user without a password is matched once by
verified email. auth.mode mixed and oidc (admins keep a password way in), role from adminGroups,
allowedGroups, signing out at the provider. Settings -> Sign-in with Test. Tested against a fake
provider with RS256 and ES256 keys.