Fix JsonType.streamAsLines() for empty Stream

When the stream is empty, we still need to send some response body when used with an http server.

The fix for this is to always append a blank empty line to the content. Client consumers are expected to ignore empty content (filter empty lines).

Author: rob-bygrave

blackbox-test/src/test/java/org/example/customer/stream/StreamBasicTest.java

@@ -27,7 +27,7 @@ void streamAsLines_toJsonFromJson() {
     JsonType<Stream<MyBasic>> streamType = type.streamAsLines();
 
     String asJson = streamType.toJson(basics.stream());
-    String expected = "{\"id\":1,\"name\":\"a\"}\n{\"id\":2,\"name\":\"b\"}\n{\"id\":3,\"name\":\"c\"}\n";
+    String expected = "{\"id\":1,\"name\":\"a\"}\n{\"id\":2,\"name\":\"b\"}\n{\"id\":3,\"name\":\"c\"}\n\n";
     assertThat(asJson)
       .describedAs("expect new line delimited json content")
       .isEqualTo(expected);

jsonb/src/main/java/io/avaje/jsonb/core/StreamAdapter.java

@@ -30,6 +30,7 @@ public void toJson(JsonWriter writer, Stream<T> stream) {
           elementAdapter.toJson(writer, bean);
           writer.writeNewLine();
         });
+        writer.writeNewLine();
       } else {
         writer.beginArray();
         stream.forEach(bean -> elementAdapter.toJson(writer, bean));