private static Class<?> validateClientType(Class<?> clientType) {
        if (clientType != WebClient.class && clientType != HttpClient.class &&
            clientType != BlockingWebClient.class && clientType != RestClient.class) {
            throw new IllegalArgumentException(
                    "clientType: " + clientType +
                    " (expected: " + WebClient.class.getSimpleName() + ", " +
                    BlockingWebClient.class.getSimpleName() + ", " + RestClient.class.getSimpleName() + " or " +
                    HttpClient.class.getSimpleName() + ')');
        }

        return clientType;
    }
Returns a new {@link Bootstrap} for connecting to a {@link io.netty.channel.unix.DomainSocketAddress}.
The returned {@link Bootstrap} has its {@link ChannelFactory}, {@link AddressResolverGroup} and
socket options pre-configured.
core/src/main/java/com/linecorp/armeria/client/HttpClientFactory.java