DSL: Support Application Event registration

Application can publish an event which should create an HTTP hook or API call to provide a way to trig application actions externally.
There should be a corresponding DSL structure which binds event with application workflow.
Here is an example in pseudocode:
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class Application
  BindEvent:
    -"onScale": $.onScale()

 Workflows:
    onScale:
      - do something
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As a result API service should expose an http hook like
http://murano-api:8082/event/<env_id>/<app_id>/<signed_unique_eventURI>/onScale

This http hook can be with or without authentication.