Update documentation to reflect that TestServer no longer enables Cassandra and Clustering by default

[TimMoore]

As raised by @mihbor on 1818b3d#commitcomment-19935097

If I understand correctly SetupImpl and therefore TestServer.defaultSetup() now default to cluster and cassandra disabled. If so, the documentation at http://www.lagomframework.com/documentation/1.2.x/java/Test.html
and the comment in line 162 need updating:

lagom/testkit/javadsl/src/main/scala/com/lightbend/lagom/javadsl/testkit/ServiceTest.scala

Line 162 in ccd4fa9

* The default `Setup` configuration, which has persistence enabled.

[mihbor]

Also, I noticed Kafka support is always disabled:

lagom/testkit/javadsl/src/main/scala/com/lightbend/lagom/javadsl/testkit/ServiceTest.scala

Line 266 in ccd4fa9

disableModules(b2, KafkaClientModule, KafkaBrokerModule)

Probably needs mentioning in the docs too.

And btw, how to test services with kafka? Is it not supported yet? Are there plans to add support for it?

I added a topic subscriber to my service as in http://www.lagomframework.com/documentation/1.2.x/java/MessageBrokerApi.html#subscribe-to-a-topic
and suddenly existing tests fail because guice can't inject dependencies any more:

com.google.inject.CreationException: Unable to create injector, see the following errors:
1) Error injecting constructor, java.lang.IllegalStateException: Attempt to get a topic, but there is no TopicFactory provided to implement it. You may need to add a dependency on lagom-javadsl-kafka-broker to your projects dependencies.

even though the dependency on lagom-javadsl-kafka-broker is present.

EDIT: I should add that I'm subscribing to a topic from the same service that is declaring the topic, in case it makes any difference. I also tried calling bindClient on the service's own interface in the configure method to see if that helps but it just gave a different injection exception.

[TimMoore]

@mihbor we have been discussing among the team how best to support testing services with Kafka

You can see how we're doing it in one of our example apps here: lagom/online-auction-java#11 (essentially stubbing out the topic factory in the tests).

We're open to feedback about the best approach for tests with Kafka (particularly if you want to do integration tests against a running Kafka instance).