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It would not be hard to introduce a 1:Many relationship between notifications and templates/messages. This could enable sending multiple notifications in response to one notification event. In workspaces, an example of this might be sending one note to the QA team for a capability reaching that step while also sending a notification to the user that the processing has entered the quality assurance state. The workspaces application wouldn't need to intentionally send two notifications, but two would get sent out by the notification system.
Implementation Notes
A more rigorous conception:
Design questions
Consider the three protocols SMS, Email and Slack. Of these, one is simply body text (SMS); the other two have additional message attributes. Email has arbitrary headers, but some of those headers are essentially mandatory (From, Subject). Slack has a mandatory text field but can actually accept a complex JSON object with many "blocks" and create a high level of interactivity. On top of this, two of these protocols need a recipient to be explicitly identified (SMS and Email) and the other does not.
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