Make fetching of Job variables more convenient and DRY

Instead of repeating variable names in the fetchVariables property of the @ZeebeWorker annotation and then later in the actual variable access, e.g.

  @ZeebeWorker(type = "myType", fetchVariables = { "orderId" } )
  public void handleJob(final JobClient client, final ActivatedJob job) {
    String orderNumber = (String) job.getVariablesAsMap().get("orderId");
  }

we could keep it DRY (Don’t Repeat Yourself) and convenient with an argument list, e.g.

  @ZeebeWorker(type = "myType")
  public void handleJob(final JobClient client, final ActivatedJob job, String orderId) {
  }

Type casting would also be done implicitly here. Not sure if the additional parameter would have to be annotated to make this work.

[berndruecker]

Or probably?

@ZeebeWorker(type = "myType") public void handleJob(final JobClient client, final ActivatedJob job, @ZeebeVariable String orderId) { }

[berndruecker]

I generally like that direction, but I am worried that this allows configuring wired things:

@ZeebeWorker(type = "myType", fetchVariables={"a", "b"}, fetchAllVariables=true)

But maybe I am too worried 😉 The above situation could raise an exception during startup as being invalid - or we simply say that “fetchAllVariables=true” always wins - which still make sense I guess