default void ensureUserIdentity(final UserDesc userDesc) {
        throw new UnsupportedOperationException("Ensuring user identities manually is not supported");
    }
Allows an identity provider to manually add a userIdentity, e.g. so it is available
in stroom for permissions to be granted to it prior to the user logging in.
If the userIdentity is present, its displayName and fullName will be updated using
the values from userIdentity.
stroom-security/stroom-security-api/src/main/java/stroom/security/api/UserIdentityFactory.java