input: Write a python function to generate a JSON string with the current UTC time.
  assert "currentTime" in time_json_string()
  assert isinstance(json.loads(time_json_string()), dict)
  assert "T" in json.loads(time_json_string())["currentTime"]
output: def time_json_string():
      import json
      from datetime import datetime, timezone
  
      current_utc_time = datetime.now(timezone.utc).isoformat()
      return json.dumps({"currentTime": current_utc_time})