@SuppressWarnings("unchecked")
    public static String getUserIdFromIdentities(final String identities) {
        String userId = null;
        try {
            if (identities != null) {
                final JSONParser jsonParser = new JSONParser();
                final List<Object> list = (List<Object>) jsonParser.parse(identities, CONTAINER_FACTORY);
                if (list != null && list.size() > 0) {
                    final Map<String, Object> identity = (Map<String, Object>) list.get(0);
                    userId = (String) identity.get(USER_ID);
                }
            }
        } catch (final ParseException | RuntimeException e) {
            LOGGER.debug(e.getMessage(), e);
        }
        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