[SSE] Relax SSE Accept Header Validation (#273)

* relax sse accept header

Now will not throw an exception for multivalue accept headers

* Update SseHandler.java

Author: SentryMan

avaje-jex/src/main/java/io/avaje/jex/http/sse/SseHandler.java

@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.util.Optional;
 import java.util.function.Consumer;
 
 import io.avaje.jex.core.Constants;
@@ -22,9 +23,13 @@ final class SseHandler implements ExchangeHandler {
   @Override
   public void handle(Context ctx) throws Exception {
 
-    if (!TEXT_EVENT_STREAM.equals(ctx.header(Constants.ACCEPT))) {
-      throw new BadRequestException("SSE Requests must have an 'Accept: text/event-stream' header");
-    }
+    Optional.ofNullable(ctx.header(Constants.ACCEPT))
+        .filter(s -> s.contains(TEXT_EVENT_STREAM))
+        .orElseThrow(
+            () ->
+                new BadRequestException(
+                    "SSE Requests must have an 'Accept: text/event-stream' header"));
+
     final var exchange = ctx.exchange();
     final var headers = exchange.getResponseHeaders();
     headers.add(Constants.CONTENT_TYPE, TEXT_EVENT_STREAM);