Box 1: DeployIfNotExists -
DeployIfNotExists executes a template deployment when the condition is met.
Box 2: Template -
The details property of the DeployIfNotExists effects has all the subproperties that define the related resources to match and the template deployment to execute.
Deployment [required]
This property should include the full template deployment as it would be passed to the Microsoft.Resources/deployment
References:
https://docs.microsoft.com/en-us/azure/governance/policy/concepts/effects
