Documentation of stage events

[johannes-b]

In the https://github.com/keptn/spec/blob/master/cloudevents.md a section should be provided to explain the stage events fired by the shipyard-controller. Given the below example of a shipyard, the following stage events are fired:

• sh.keptn.event.dev.artifact-delivery.triggered
• sh.keptn.event.dev.artifact-delivery.finished
• sh.keptn.event.staging.artifact-delivery.triggered
• sh.keptn.event.staging.artifact-delivery.finished

apiVersion: "spec.keptn.sh/0.2.0"
kind: "Shipyard"
metadata:
  name: "shipyard-sockshop"
spec:
  stages:
    - name: "dev"
      sequences:
        - name: "artifact-delivery"
          tasks:
            - name: "deployment"
            - name: "test"
            - name: "evaluation"
            - name: "release"

    - name: "staging"
      sequences:
        - name: "artifact-delivery"
          triggers:
            - "dev.artifact-delivery.finished"
          tasks:
            - name: "deployment"
            - name: "test"
            - name: "evaluation"
            - name: "release"

Task: Provide documentation to explain:

• The pattern of a stage event follows this format: sh.keptn.event.{stage}.{seqeunece}.{triggered | finished}
• The result, status, and message properties represent the properties from the last successfully executed task in the sequence.