public final HttpAsyncClientBuilder setProxyAuthenticationStrategy(
            final AuthenticationStrategy proxyAuthStrategy) {
        this.proxyAuthStrategy = proxyAuthStrategy;
        return this;
    }
Sets {@link AuthenticationStrategy} instance for proxy
authentication.

@return this instance.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncClientBuilder.java