how to dynamically route a log event to a sink or transform based on a log key

Question

I always want to route incoming log events to an output which is identified by value of a specific key in event. According to the docs, if route transform supported datadog template syntax my route configuration would have been somethong like this, but it doesn't:

route: 
  - {{.key}} : true

Any idea how can I do this without explicitly declaring routes for all possible values for "key"?