Publish Logstash Java dependencies to Maven central

[nielsbasjes]

This is a follow up of issue #9215 as discussed @danhermann

Support for Java based plugins is now GA.

The current problem is that actually building a plugin currently requires downloading and building Logstash locally in order to get the needed dependencies.

The desire is to have those dependencies available on maven central so that building such a plugin can be done in something like Travis or Gitlab CI.

[nielsbasjes]

@danhermann It has been a few months since Java based plugins became GA.
Do you have any indication when this is going to be picked up?

[danhermann]

@nielsbasjes, we still have this on our list of things to do, but the work has not been scheduled for a particular release, yet.

[nielsbasjes]

FYI: I have figured out an automated way to get the needed dependency into the build that works in Travis.

Effectively I have written a script that downloads the current logstash distribution, extracts the logstash-core.jar from it and installs it locally in the maven repository.

https://github.com/nielsbasjes/yauaa/blob/master/udfs/logstash/logstash-dependency/download-logstash.sh
Sadly this means downloading ~150MiB to get a dependency jar that is only ~0.6MiB.

[nielsbasjes]

3 years after GA this has not been fixed properly.
So I'm dropping support for Logstash.