Azure Policy to enforce Tag & Pattern

gistfile1.txt

{
  "properties": {
    "displayName": "Require a tag, value and pattern",
    "policyType": "Custom",
    "mode": "Indexed",
    "description": "Enforces a required tag and its value. Does not apply to resource groups.",
    "metadata": {
      "category": "Tags",
      "createdBy": "10742b83-5bcb-45ba-9a2b-8a953928fc04",
      "createdOn": "2020-04-01T16:11:01.7403115Z",
      "updatedBy": "10742b83-5bcb-45ba-9a2b-8a953928fc04",
      "updatedOn": "2020-04-01T16:18:18.6767553Z"
    },
    "parameters": {
      "tagName": {
        "type": "String",
        "metadata": {
          "displayName": "Tag Name",
          "description": "Name of the tag, such as 'deptcode'"
        }
      },
      "tagValue": {
        "type": "String",
        "metadata": {
          "displayName": "Tag Value",
          "description": "pattern of the tag, such as 'ABC???'"
        }