private static ResponseHeaders sanitizeHeaders(ResponseHeaders headers) {
        if (headers == defaultHttpHeaders) {
            return headers;
        }
        return ensureContentType(ensureHttpStatus(headers));
    }
Creates a new Server-Sent Events stream of the specified {@code content}.

@param headers the HTTP headers supposed to send
@param sse the {@link ServerSentEvent} object supposed to send as contents
@param trailers the HTTP trailers
core/src/main/java/com/linecorp/armeria/server/streaming/ServerSentEvents.java