jetty: Configuring jetty max header size

- fix #2909
- allow to configure custom jetty options

```java
{
   use(
     new JettyServer()
         .configure(http -> {
             http.setRequestHeaderSize(16 * 1024);
         })
   )
}
```

modules/jooby-jetty/src/main/java/io/jooby/jetty/JettyServer.java

@@ -61,6 +61,8 @@ public class JettyServer extends io.jooby.Server.Base {
 
  private ServerOptions options = new ServerOptions().setServer("jetty").setWorkerThreads(THREADS);
 
+ private Consumer<HttpConfiguration> httpConfigurer;
+
  public JettyServer(@NonNull ThreadPool threadPool) {
  this.threadPool = threadPool;
  }
@@ -83,6 +85,17 @@ public String getName() {
  return "jetty";
  }
 
+ /**
+ * Applies custom configuration. This applies to HTTP and HTTPS (when enable).
+ *
+ * @param configurer Configurer.
+ * @return This server.
+ */
+ public JettyServer configure(Consumer<HttpConfiguration> configurer) {
+ this.httpConfigurer = configurer;
+ return this;
+ }
+
  @NonNull @Override
  public io.jooby.Server start(Jooby application) {
  try {
@@ -109,7 +122,6 @@ public io.jooby.Server start(Jooby application) {
  options.isHttp2() == Boolean.TRUE ? new JettyHttp2Configurer() : null;
 
  HttpConfiguration httpConf = new HttpConfiguration();
- // TODO: we might need to remove legacy with default
  httpConf.setUriCompliance(UriCompliance.LEGACY);
  httpConf.setOutputBufferSize(options.getBufferSize());
  httpConf.setOutputAggregationSize(options.getBufferSize());
@@ -118,6 +130,10 @@ public io.jooby.Server start(Jooby application) {
  httpConf.setSendServerVersion(false);
  httpConf.setMultiPartFormDataCompliance(MultiPartFormDataCompliance.RFC7578);
 
+ if (httpConfigurer != null) {
+ httpConfigurer.accept(httpConf);
+ }
+
  List<ConnectionFactory> connectionFactories = new ArrayList<>();
  connectionFactories.add(new HttpConnectionFactory(httpConf));
  if (http2 != null) {