public static String getSubject(final JwtClaims jwtClaims) {
        LOGGER.debug(() -> {
            try {
                return "Subject=" + jwtClaims.getSubject();
            } catch (final MalformedClaimException e) {
                LOGGER.debug(e.getMessage(), e);
            }
            return "MalformedClaimException";
        });

        String subject = null;
        try {
            subject = jwtClaims.getSubject();
        } catch (final MalformedClaimException e) {
            LOGGER.debug(e.getMessage(), e);
        }
        return subject;
    }
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