@Streaming(false)
        @Get("/serverSentEventFuture")
        @ResponseConverter(ServerSentEventResponseConverterFunction.class)
        public CompletableFuture<ServerSentEvent> serverSentEventFuture() {
            return UnmodifiableFuture.completedFuture(ServerSentEvent.ofData("serverSentEventFuture"));
        }
A mock service for testing {@link ServerSentEventResponseConverterFunction}.
core/src/test/java/com/linecorp/armeria/internal/server/annotation/ResponseStreamingTest.java