WebSocket Encoder has to be explicitly registered for reflection

[michalszynkiewicz]

Describe the bug
Using a custom encoder in the native mode fails with a failure on reflective instantiation.
A user needs to use @RegisterForReflection to make it work.

Expected behavior
I'd expect all encoders and decoders to be registered for reflection automatically

Actual behavior
Application fails to instantiate a custom encoder for a web socket server.

To Reproduce
Steps to reproduce the behavior:

1. git clone https://github.com/michalszynkiewicz/failing-email-service
2. mvn clean package -Pnative
3. go with your browser to http://localhost:8080

Environment (please complete the following information):

• Output of uname -a or ver:

Linux t580 5.0.17-200.fc29.x86_64 #1 SMP Mon May 20 15:39:10 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

• Output of java -version:

java version "1.8.0_201"
Java(TM) SE Runtime Environment (build 1.8.0_201-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.201-b09, mixed mode)

• GraalVM version (if different from Java):
  RC15
• Quarkus version or git rev: 0.16.0

Additional context
The stack trace:

UT026001: Unable to instantiate endpoint: java.lang.RuntimeException: java.lang.InstantiationException: Type `com.example.JsonEncoder` can not be instantiated reflectively as it does not have a no-parameter constructor or the no-parameter constructor has not been added explicitly to the native image.
        at io.quarkus.arc.runtime.ArcDeploymentTemplate$DefaultInstanceFactory.create(ArcDeploymentTemplate.java:152)
        at io.quarkus.undertow.runtime.UndertowDeploymentTemplate$6$1.createInstance(UndertowDeploymentTemplate.java:414)
        at io.undertow.websockets.jsr.EncodingFactory.createEncoding(EncodingFactory.java:126)
        at io.undertow.websockets.jsr.EndpointSessionHandler.onConnect(EndpointSessionHandler.java:121)
        at io.undertow.websockets.jsr.JsrWebSocketFilter$1.handleUpgrade(JsrWebSocketFilter.java:165)
        at io.undertow.server.protocol.http.HttpReadListener.exchangeComplete(HttpReadListener.java:385)
        at io.undertow.server.protocol.http.HttpServerConnection.exchangeComplete(HttpServerConnection.java:232)
        at io.undertow.server.HttpServerExchange.invokeExchangeCompleteListeners(HttpServerExchange.java:1279)
        at io.undertow.server.HttpServerExchange.terminateResponse(HttpServerExchange.java:1563)
        at io.undertow.server.Connectors.terminateResponse(Connectors.java:147)
        at io.undertow.server.protocol.http.HttpTransferEncoding$3.handleEvent(HttpTransferEncoding.java:197)
        at io.undertow.server.protocol.http.HttpTransferEncoding$3.handleEvent(HttpTransferEncoding.java:195)
        at io.undertow.conduits.HeadStreamSinkConduit.exitFlush(HeadStreamSinkConduit.java:192)
        at io.undertow.conduits.HeadStreamSinkConduit.flush(HeadStreamSinkConduit.java:133)
        at org.xnio.conduits.ConduitStreamSinkChannel.flush(ConduitStreamSinkChannel.java:162)
        at io.undertow.channels.DetachableStreamSinkChannel.flush(DetachableStreamSinkChannel.java:119)
        at org.xnio.channels.Channels.flushBlocking(Channels.java:63)
        at io.undertow.servlet.spec.ServletOutputStreamImpl.close(ServletOutputStreamImpl.java:618)
        at io.undertow.servlet.spec.HttpServletResponseImpl.closeStreamAndWriter(HttpServletResponseImpl.java:486)
        at io.undertow.servlet.spec.HttpServletResponseImpl.responseDone(HttpServletResponseImpl.java:575)
        at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:351)
        at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
        at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
        at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
        at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
        at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
        at io.quarkus.undertow.runtime.UndertowDeploymentTemplate$7$1$1.call(UndertowDeploymentTemplate.java:469)
        at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
        at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
        at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
        at io.undertow.server.Connectors.executeRootHandler(Connectors.java:364)
        at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
        at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
        at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:2011)
        at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1538)
        at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1395)
        at org.jboss.threads.DelegatingRunnable.run(DelegatingRunnable.java:29)
        at org.jboss.threads.ThreadLocalResettingRunnable.run(ThreadLocalResettingRunnable.java:32)
        at java.lang.Thread.run(Thread.java:748)
        at org.jboss.threads.JBossThread.run(JBossThread.java:479)
        at com.oracle.svm.core.thread.JavaThreads.threadStartRoutine(JavaThreads.java:473)
        at com.oracle.svm.core.posix.thread.PosixJavaThreads.pthreadStartRoutine(PosixJavaThreads.java:193)
Caused by: java.lang.InstantiationException: Type `com.example.JsonEncoder` can not be instantiated reflectively as it does not have a no-parameter constructor or the no-parameter constructor has not been added explicitly to the native image.
        at java.lang.Class.newInstance(DynamicHub.java:740)
        at io.quarkus.arc.runtime.ArcDeploymentTemplate$DefaultInstanceFactory.create(ArcDeploymentTemplate.java:144)
        ... 41 more