Is Query perhaps the way to do this?
- The HTTP handler basically polls for the state of the workflow
- Workflow sets the query result when a task requiring an interrupt is encountered. The query result contains the signal to be sent when the task is completed.
- HTTP handler presents the page with the appropriate signal embedded within a callback/post URL.
The other option would be to use Update, but the goal here isn’t to change the state of the workflow, so I am not sure it is appropriate. The answer here appears to indicate it is the way to go though - Receive a workflow signal from a client