How to use notify with orquesta workflow and jinja expression support?

Issue: Not able to notify in slack channel with workflow output/stdout. How to use workflow context and variable in notify parameter, without writing for each of the task in the workflow

Workflow-meta.yaml

---
description: A Nessus scanner reporter validator workflow
enabled: true
runner_type: orquesta
entry_point: workflows/nessus_report_validation_workflow.yaml
name: nessus_report_validation_workflow
pack: st2pack_poc
notify:
  on-complete:
    routes:
      - slack
    message: "Action has finished"
  on-success:
    routes:
      - slack
    message: "Succeeded: {{action_results.stdout}}"
  on-failure:
    routes:
      - slack
    message: |
     Yikes!! It failed. {{ stdout }} {{ result().stdout }} <% ctx() %> <% result().issue_key %>  <% stdout %>!!
parameters:
...

Slack channel output:

Start with Workflow-meta.yaml and workflows/nessus_report_validation_workflow.yaml, then trace how the notify messages render expressions for the Slack route. Reproduce the workflow and compare action_results, stdout, result(), and ctx() in the notification output; done requires a documented or tested way to expose the workflow result in on-success and on-failure messages.