presto-spi/src/main/java/io/prestosql/spi/security/ConnectorIdentity.java/ConnectorIdentity/ConnectorIdentity
class ConnectorIdentity:    public ConnectorIdentity(String user, Optional<Principal> principal, Optional<SelectedRole> role, Map<String, String> extraCredentials)
    {
        this.user = requireNonNull(user, "user is null");
        this.principal = requireNonNull(principal, "principal is null");
        this.role = requireNonNull(role, "role is null");
        this.extraCredentials = unmodifiableMap(new HashMap<>(requireNonNull(extraCredentials, "extraCredentials is null")));
    }