Add support for Webhooks

[codenio]

ISSUE TYPE

• Feature Pull Request

SUMMARY

Modify return type as pointer:

This commit,

• modifies return type of GetLastSeenSlackMessage to pointers.

Add support for Webhooks:

This Commit,

• Adds support for event notifications through Wehbook
• updates configs in all yaml files
• updated helm charts
• adds unit tests for webhook notifier
• adds integration test webhook notifier
• adds test/webhook package to enable integration testing.

Preview:

{
  "meta": {
    "kind": "Pod",
    "name": "command-app-1",
    "namespace": "default",
    "cluster": "demo"
  },
  "status": {
    "type": "create",
    "level": "info",
    "reason": "",
    "messages": [
      "Resource created\n"
    ]
  },
  "summary": "Pod `command-app-1` in of cluster `demo`, namespace `default` has been created:\n```Resource created\nRecommendations:\n- :latest tag used in image 'debian' of Container 'command-demo-container' should be avoided.\n```",
  "timestamp": "2019-08-30T22:29:04+05:30",
  "recommendations": [
    ":latest tag used in image 'debian' of Container 'command-demo-container' should be avoided.\n"
  ]
}

[sanketsudake]

@aananthraj
Lets add unit tests and integration tests as well. We can mock webhook URL and notifier would call that webhook URL with payload. We can verify cross check payload received on Webhook and sent from notifier.

You can also refer integration tests recently added by @PrasadG193

[codenio]

@sanketsudake, @PrasadG193 made those requested changes.

[PrasadG193]

Minor comment, can we rename test/webhooktest package to test/webhook to maintain consistency in the naming format of all test/* packages

[codenio]

Sure, lets maintain the same.
Let know in case of further changes (if any)

[codenio]

made those request changes.
It is ready now, let's get it merged.

[PrasadG193]

Looks good for now, we might need to add support for the self-signed certificates in future