Add support for event tasks

[boma96]

[WorkflowMetadata(OwnerEmail = "test@test.com")]
public class EventTaskWorkflow : Workflow<EventTaskWorkflow, EventTaskWorkflowInput, EventTaskWorkflowOutput>
{
    public class EventTaskPayload : IRequest<EventTaskModelOutput>
    {
        public string PayloadParam { get; set; }
    }

    public EventTaskModel<EventTaskPayload> EventTask { get; set; }

    public EventTaskWorkflow(WorkflowDefinitionBuilder<EventTaskWorkflow, EventTaskWorkflowInput, EventTaskWorkflowOutput> builder)
        : base(builder) { }

    public override void BuildDefinition()
    {
        _builder.AddTask(wf => wf.EventTask, wf => new() { PayloadParam = "param" }, "conductor:event");
    }
}