ExpressRoute should not use Authorization keys: Policy does not exists today

Details of the scenario you tried and the problem that is occurring

The ExpressRoute authorization keys are used for cross-subscription/tenant networking.
This should be controlled by a defined process owned by the network team and any attempt to create an authorization key without following the process should be denied or audited.

Suggested solution to the issue

Implement the suggest policy

Suggested policy

{
  "properties": {
    "displayName": "ExpressRoute should not use Authorization keys",
    "policyType": "BuiltIn",
    "mode": "Indexed",
    "description": "This policy denies the creation of Authorization keys for the ExpressRoute. Authorization keys are used to enable cross-subscription/cross-tenant networking functionality to the ExpressRoute. This should be reviewed by the network security team. https://learn.microsoft.com/en-us/azure/expressroute/expressroute-howto-linkvnet-portal-resource-manager",
    "metadata": {
      "version": "1.0.0",
      "category": "Network"
    },
    "parameters": {
        "effect": {
            "type": "String",
            "metadata": {
                "displayName": "Effect",
                "description": "Deny or Audit the use of authorization key for ExpressRoute"
            },
            "allowedValues": [
                "Deny",
                "Audit",
                "Disabled"
            ],
            "defaultValue": "Deny"
        }
    },
    "policyRule": {
      "if": {
        "allOf": [
          {
            "field": "type",
            "equals": "Microsoft.Network/expressRouteCircuits"
          },
          {
            "count": {
              "field": "Microsoft.Network/expressRouteCircuits/authorizations[*]"
            },
            "greaterOrEquals": 1
          }
        ]
      },
      "then": {
        "effect": "[parameters('effect')]"
      }
    }
  },
  "id": "/providers/Microsoft.Authorization/policyDefinitions/14856350-e609-4aa5-a34f-b2f59fc92173",
  "name": "14856350-e609-4aa5-a34f-b2f59fc92173"
}

The issue provides the complete suggested Azure Policy JSON, but names no repository file, test, or entry point. Start by locating the built-in policy definition layout in this repository and compare nearby Network policies. Done means the ExpressRoute authorization-key policy is added using the supplied rule and metadata.