@Override
    public String toString() {
        return "ServiceUserIdentity{" +
               "id='" + id + '\'' +
               ", updatableToken=" + updatableToken +
               '}';
    }
User identity for a service user for this application to authenticate with other
applications on the same IDP realm. I.e. Stroom's processing user.
This user uses the client credentials flow.
stroom-security/stroom-security-common-impl/src/main/java/stroom/security/common/impl/ServiceUserIdentity.java