feat: add additional notification policy logic

[RoseSecurity]

What and Why

Note

Feel free to accept or close this PR. We are still evaluating if this logic has solved our webhook failures

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• This is an attempt to resolve the failing Spacelift webhooks detailed in fix(policy.rego): Use DataDog format for metrics units #11 :

Webhook "datadog-metrics-datadoghq-com" failed with an error: could not deliver webhook payload: Post "https://api.datadoghq.com/api/v2/series": EOF

• Adds additional logic to the notification policy to assess if the payload is empty. Only sends the webhook if the the payload is non-empty
• Runs opa fmt on rego policy

References

• Policy Docs