Skip scheduling if timeout is zero (i.e. execute immediately)

src/activities/Elsa.Activities.Timers/Activities/Timer/Timer.cs

@@ -31,6 +31,9 @@ namespace Elsa.Activities.Timers
         {
             if (context.WorkflowExecutionContext.IsFirstPass)
                 return Done();
+
+            if (Timeout == Duration.Zero)
+                return Done();
             
             ExecuteAt = _clock.GetCurrentInstant().Plus(Timeout);
 

src/core/Elsa.Abstractions/Services/Models/ProcessFault.cs

@@ -13,7 +13,7 @@
 
         public Elsa.Models.WorkflowFault ToInstance()
         {
-            return new Elsa.Models.WorkflowFault
+            return new()
             {
                 FaultedActivityId = FaultedActivity?.Id,
                 Message = Message