Implement basic testing for the kafka output module

[Popsiclestick]

This PR is for #10652

I've implemented the same TCP connection test found in the elasticsearch output test. This is a basic test.

Example output below

:; go build && ./filebeat test output -c kafka-filebeat.yml
TLS... WARN Kafka output doesn't support TLS testing
Kafka: localhost:9092...
  parse host... OK
  dns lookup... OK
  addresses: ::1, 127.0.0.1
  dial up... OK
Kafka: 127.0.0.1:9092...
  parse host... OK
  dns lookup... OK
  addresses: 127.0.0.1
  dial up... OK
Kafka: 0.0.0.0:9092...
  parse host... OK
  dns lookup... OK
  addresses: 0.0.0.0
  dial up... OK

Note:
The test will function whether or not the kafka server requires TLS. I did look to implement the transport.TestTLSDialer as well. But the TLS config objects which are passed don't look to be standardized between outputs. Kafka morphs the original object to integrate with sarama. The kafka client only has access to sarama.Config which doesn't contain the original object to perform tlscommon.LoadTLSConfig. Though I am likely missing something.

I am happy to implement any recommendations.

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[jsoriano]

@Popsiclestick this is looking good, thanks! Before merging this change you will have to sign the CLA.

To obtain the TLS configuration you may try to do the reverse operation of tlscommon.BuildModuleConfig, with the TLS config stored in the sarama config object. But I am not sure if at this point all the information is available.

[jsoriano]

jenkins, test this

[Popsiclestick]

I signed it. Strange though, I had already signed the agreement last week. Not sure, but hopefully it works now.

[jsoriano]

@Popsiclestick sorry, it seems that there was some kind of problem with CLA checker, could you try to sign it again?

[Popsiclestick]

Signed again :)

[jsoriano]

@Popsiclestick right, it seems to be working now 🎉

Do you want to give another try to TLS config? If not I think this is ready to go, and TLS can be added later.

[Popsiclestick]

Wooh! @jsoriano

I think we should merge this in for now. If I get some more time in the future, I can look at trying to get TLS added later.

[jsoriano]

Thanks!

[jsoriano]

@Popsiclestick oh sorry, I almost forgot it! I think this change should have an entry in CHANGELOG.next.asciidoc, could you add it?

[Popsiclestick]

@jsoriano Everything look good now? 👍

[jsoriano]

jenkins, test this

[jsoriano]

@Popsiclestick looks good, thanks! I'll merge it when everything is green 🙂