Nextcloud: Group restriction bypass via bearer token in user_oidc (SETTING_RESTRICT_LOGIN_TO_GROUPS not enforced in Backend::getCurrentUserId)

A security inconsistency was identified in the useroidc app where group-based login restrictions were enforced in the browser OIDC flow but not in bearer token validation. This could have allowed users outside whitelisted groups to access the Nextcloud API with a valid bearer token...