public static String removePrefix(final String userId) {
        if (userId != null) {
            int index = userId.indexOf(CORP_PREFIX);
            if (index != -1) {
                return userId.substring(CORP_PREFIX.length());
            }
        }
        return userId;
    }
Gets the unique ID that links the identity on the IDP to the stroom_user.
Maps to the 'name' column in stroom_user table.
stroom-security/stroom-security-common-impl/src/main/java/stroom/security/common/impl/JwtUtil.java