move code to src/test

* so that it compiles and tests pass
* fix some additional snip references in getting started

akka-docs/src/main/java/jdocs/cluster/TransformationFrontend.java

@@ -1,44 +0,0 @@
-package jdocs.cluster;
-
-import static jdocs.cluster.TransformationMessages.BACKEND_REGISTRATION;
-
-import java.util.ArrayList;
-import java.util.List;
-
-import jdocs.cluster.TransformationMessages.JobFailed;
-import jdocs.cluster.TransformationMessages.TransformationJob;
-import akka.actor.ActorRef;
-import akka.actor.Terminated;
-import akka.actor.AbstractActor;
-
-//#frontend
-public class TransformationFrontend extends AbstractActor {
-
-  List<ActorRef> backends = new ArrayList<ActorRef>();
-  int jobCounter = 0;
-
-  @Override
-  public Receive createReceive() {
-    return receiveBuilder()
-      .match(TransformationJob.class, job -> backends.isEmpty(), job -> {
-        getSender().tell(
-          new JobFailed("Service unavailable, try again later", job),
-            getSender());
-      })
-      .match(TransformationJob.class, job -> {
-        jobCounter++;
-        backends.get(jobCounter % backends.size())
-          .forward(job, getContext());
-      })
-      .matchEquals(BACKEND_REGISTRATION, x -> {
-        getContext().watch(getSender());
-        backends.add(getSender());
-      })
-      .match(Terminated.class, terminated -> {
-        backends.remove(terminated.getActor());
-      })
-      .build();
-  }
-
-}
-//#frontend