Generate CheckNameAvailable response assertion

[tianxchen-ms]

Step should fail when CheckNameAvailable response failed.

"liveResponse": {
    "statusCode": "200",
    "headers": {
      "Cache-Control": "no-cache",
      "Pragma": "no-cache",
      "Content-Length": "181",
      "Content-Type": "application/json; odata.metadata=minimal",
      "Expires": "-1",
      "x-ms-request-id": "c4cee406-6e38-48ed-9e8d-e2c0f4e2d6b0",
      "x-ms-client-request-id": "1c1f50dc-f6d1-4412-9bcb-357842adf4c5",
      "OData-Version": "4.0",
      "Server": "Microsoft-HTTPAPI/2.0",
      "x-ms-ratelimit-remaining-subscription-writes": "1199",
      "x-ms-correlation-request-id": "4129d14c-4569-4e9f-a69e-59a136b8d3ec",
      "x-ms-routing-request-id": "WESTUS:20230203T023359Z:4129d14c-4569-4e9f-a69e-59a136b8d3ec",
      "Strict-Transport-Security": "max-age=31536000; includeSubDomains",
      "X-Content-Type-Options": "nosniff",
      "Date": "Fri, 03 Feb 2023 02:33:58 GMT"
    },
    "body": {
      "nameAvailable": false,
      "reason": "Invalid",
      "message": "The Media Account account name should be between 3 and 24 characters and may contain only lowercase letters and numbers."
    }
  }