FlowSseClient add sse connect headers

[qngl]

Please do a quick search on GitHub issues first, the feature you are about to request might have already been requested.

Expected Behavior

public void subscribe(String url, String sseHeaders, SseEventHandler eventHandler) {
	HttpRequest request = HttpRequest.newBuilder()
		.uri(URI.create(url))
		.header("Accept", "text/event-stream")
		.header("Cache-Control", "no-cache")
                .headers(sseHeaders)
		.GET()
		.build();

Current Behavior

public void subscribe(String url, SseEventHandler eventHandler) {
	HttpRequest request = HttpRequest.newBuilder()
		.uri(URI.create(url))
		.header("Accept", "text/event-stream")
		.header("Cache-Control", "no-cache")
		.GET()
		.build();

Context

No way to do authentication for the SSE connection

[renxiawang]

Duplicate of #68 ?