Reserved keyword that gets workflow IDs similar to invoker

[nahiyan-yasaar-selise]

Currently there's no way to know if a workflow was triggered by a user or a particular workflow. We would like two reserved keywords, one that holds the current workflow's ID (workflowID), another that holds the ID of the workflow that caused the trigger (triggerer?). If a user triggers a workflow due to an update invoker has the userID, but triggerer will be null, but if workflowA triggers workflowB, then triggerer in workflowB has the ID of workflowA whereas invoker should be null.

Possible benefits/use cases:

• Allows prevention of infinite loops in a clean way: we can simply have a gateway condition workflowID == triggerer that terminates early. Or if workflowA triggers workflowB and workflowB triggers workflowA, we can do a similar gateway condition.
• Allows custom branching behaviour depending on which workflow triggers a particular workflow. E.g. if workflowX is triggered by workflowA, then do one thing, but if it's triggered by workflowB do another thing.

This effectively turns workflows into pseudo-subworkflows with a built-in parameter being pre-filled.