Required parameters aren't mandatory

[joschi]

Problem description

Developers have the possibility to mark certain parameters for a pipeline functions as "required". Unfortunately, that doesn't have any effect on the functions and the pipeline parser simply ignores missing "required" parameters (and is using null for their value).

Steps to reproduce the problem

See https://community.graylog.org/t/another-try-at-pipeline-rules/1762

when
  true
then
  set_field("foobar"); // <- this should fail
end

Environment

• Pipeline Processor plugin version: 2.3.0-rc.2 and earlier