Provide CloudEvents around failed authentications for scaling triggers

[tomkerkhove]

Proposal

Event Types

• keda.scaledobject.authentication.failed.v1
• keda.scaledjob.authentication.failed.v1

Payload:

{
    "specversion" : "1.0",
    "type" : "keda.scaledobject.authentication.failed.v1",
    "subject" : "/{kubernetes-cluster-name}/{namespace}/{scaled-job/object}/{resource-name}/triggers/{trigger-name}",
    "time" : "2018-04-05T17:31:00Z",
    "datacontenttype" : "application/json",
    "data" : {
      "scaleTarget": {
         "name": "sample-workload",
         "apiVersion": "Deployment",
         "kind": "apps/v1",
      },
      "scaledObject/scaledJob": {
         "name": "sample-workload",
         "namespace": "<namespace>",
      },
      "trigger": {
         "type": "<trigger type, ie CPU>",
          "name": "<trigger-name>",
         "metadata": {
           // Trigger information
         }
      },
      "error": {
         "message": "<error message>"
      }
   }
}

Use-Case

Allow end-users to get notified when authentication to one or more scalers has failed.

Anything else?

Relates to #479