Extend outbound Notifications to call dialplan code

a discussion via Lorne Gaetz during Astricon,
Requesting that the Outbound Routes > Notification page be extended to allow it to trigger a dialplan context to allow running arbitrary code.

our specific interest in this is around creating a webhook on specific calls.
the user calls 9-1-1, triggers the emergency call outbound route
the notifications on this route trigger a set of dialplan
that dialplan runs a SET, which simply triggers a POST / HTTP webhook.

the ideal state for us here would be to trigger Slack (via slack Webhooks)
we could also then extend our own dialplan to catch Specific numbers on the route.